Consider what the "no cheating" version of the ingredient is, and get the closest thing to that, that's convenient enough for you.
For things like garlic, ginger, etc., the "no-cheating" version is to get the fresh ingredients and crush/grate them - what you end up with is a paste. The paste you can buy in jars is this stuff, with preservatives added to make them last. Some flavour will be lost.
To make powder, the paste is dried, and more flavour is lost. But the powder will keep for a long time in the cupboard.
Note that some spices take on different, desirable flavours when processed. Paprika powder has its own properties when compared to fresh paprika peppers. You'd use fresh ginger in many curries, powdered ginger in many cakes, candied ginger in some other sweet dishes. Recipes will specify what to use.
For things like black pepper, cumin, turmeric, coriander seeds, the "no-cheating" version is to get whole seeds, roast them and grind them in a spice grinder or a pestle and mortar. So buying the ready-ground version is only one step away from the ideal. Try grinding your own at least once. The extra depth and complexity of flavour is striking. But for convenience, ready-ground spices are fine.
"Roasting", for small quantities of whole dry spice, involves briefly heating them on a hot dry pan. It brings out spice flavours you don't get from just frying or boiling the spice. Of course, it's optional.
Ground spices have a shorter shelf life than whole dry spices. If you open a jar of powdered spice and it doesn't have a strong aroma, throw it away -- you might as well use dust. Whole spices have the aroma "locked away", to be released when you grind.
To make a paste, these are sometimes mixed with wet ingredients (like garlic and ginger), water and oil. That's the basis of the jars of "spice mix" you can buy in supermarkets. It's also the first step in many curry recipes -- grind your spices, mix with oil to make a paste, and gently fry before adding the onions.
I prefer Maple myself but the whole objective is to use wood species that have very tight grains and closed pores. The above that you mentioned all seem in line but as a wood worker I would think that birch would be on the bottom of my list as choices. If you look at hard woods like Oak you will notice a lot of open grain that makes the surface far to porous for this. You want it as smooth as possible so it can be cleaned well when you're done using it.
There could be other benefits that I'm not aware of so this is just an opinion from someone who works with wood a lot. When I mill birch it has a tendency to get fuzzy and it's very labor intensive to get the final piece smoothed out. I don't even bother with it any more.
Best Answer
No one device, manual or electric, is ideal for all of the tasks that you have enumerated. Many cooks will have more than one tool, depending on the job at hand.
Some spices, particularly cinnamon, are very difficult to grind effectively at home without leaving fibrous bits that may give an unpleasant mouth feel. Of course, when infusing flavor from a whole stick of cinnamon, this is not an issue.
Bottom Line
I would recommend having at least a Microplane type grater for ginger, garlic, and so on, and a rotary type electric grinder for most hard spices.
For the specialty task of making peanut butter, a blender is probably your best tool.
Morter and Pestle
Also known as a molcajete, is probably the most versatile, but most labor intensive spice grinding tool.
Microplane style grater
A grater with very fine, usually etched, openings is suitable for some tasks including:
Nutmeg Grinder
A specialty item, just for nutmeg. Most nutmeg grinders actually make very fine shavings, but it is essentially the same thing. They also have storage for nutmegs.
Blender
Electric blenders are suitable for some grinding tasks:
Some high quality blenders may also do a decent job with softer seeds like cumin seeds.
Electric rotary grinder
These are often marketed as coffee grinders, but they are extremely effective as spice grinders—however, due to lingering flavors, you want to devote one to either coffee or to spices.
Suitable for dry spices, such as cumin, black pepper, allspice, mustard seeds, and so on.
Not very effective for the hardest spices, such as cinnamon.
Note that clove oil (also found to some extent in nutmeg) can cloud plastic parts over time.
Pepper Grinder
As the name implies, ideal for black pepper, but also effective on other small spices that can fit through the mill such as mustard seeds. Also provides a small quanitity of storage. Most permit the grind size to be adjusted.
Specific Questions
Which kind of grinders allow water in them for making a paste of the spices?
Mortar and pestle, and blenders are suitable for pastes. However, you can also grind your dry spices, and then add them to a wet mixture to create a paste.
Is there some maximum and minimum capacity for each of the type of grinders?
Most home style devices are suitable only for very small quantities. The nutmeg and pepper grinders are good for teaspoon type quantities, and rotary grinders up to a few tablespoons.
Blnders have much higher capacities, but may not be effective except with very soft or frangible items. Peanut butter is one application that they do well with in larger quantities.
What are the types of manual grinders which do not require too much amount of manual power/effort?
They all require significant effort. For spices used in very small quantities, such as black pepper, that may not be noticeable.
Which kind of grinders allow us to have a fine powder of spices rather than bits?
None of the home methods will produce the very fine, even powder that you might expect from a commercial spice house. They have extremely high quality, sometimes specialized equipment, and they also sieve or screen the resulting product to ensure it is uniform, and to exclude larger bits.
Some spices are more suitable for home grinding than others. Ones that you should have little trouble with include black pepper, nutmeg, allspice, mustard seed.
Spices that are very difficult to grind at home include cinnamon.
Cumin, one of the most popular spices, is easy to grind, but difficult to get a perfectly smooth and uniform powder. It tends to have little threads and fibrous bits. In many applications this is not noticeable.