It's tough to say all your future needs will be met, but:
1/2". So, you don't run into problems with larger straight bits fitting.
Keyed. If you've had problems with slippage or spinning on smooth shanks it's the only answer. If you had spinning on hex bits, then you did something wrong. However, keyed will also fix pull-out of both smooth & hex shanks.
No, but maybe later. For what you mentioned the cheapest drills will handle it all. But, if you get into mixing 5-gallon buckets of Joint Compound or Concrete Resurfacer then you'll kill a smaller motor. However, the bigger the motor the considerably heavier the tool & you won't enjoy that at all for what you're currently doing.
Hammer Action. Not needed if you're only doing infrequent small holes & have a set of masonry bits...for most situations.
Adjustable clutch. Not needed as long as the drill is variable speed & all of them should be that you'll be considering.
Impact Action. As you say you don't want it. But, it's really-really nice. Are you sure? Have you actually tried it for 3-inch & more screws? Yummy-yummy you'll want one.
Actually, except for the 1/2" chuck & I think also for Keyed, but the Corded might be Keyed. I'd recommend the Black & Decker Matrix, it comes in Corded & Cordless. The interchangeable head will make your life so much better. I got a cordless one & all of the attachments I've got actually work better than I expected & quite well overall.
If you are drilling a hole through 3 pieces, and you do not want to purchase a 12" "twist" (metal bit) bit to do the job, which would be the way to do it.
![drill bit](https://i.stack.imgur.com/I37Ad.jpg)
If you choose to use the shorter version, there is a way to do that too. Main thing is, is to use a twist bit since it is full round so to speak and once it starts in a direction, it usually will not redirect or change it's angle of drilling. It will take a few steps to accomplish the job.
First drill the hole all the way in as far as it will possibly go, hopefully a good distance into the second piece. If possible re-chuck the drill bit into the drill so it is barely in the chuck to maximize the drill depth, after you do the initial fist bore to get that "last little bit of depth".
Remove the first piece you drilled through. Using the hole that is started in the second piece, and re-chucking the drill bit in properly continue drilling using the hole that was started in the second piece as a guide. If that does not get you all the way through, use the same method mentioned earlier to get the rest of the way through.
If the holes are needed to go through the 7 1/4" height of the beam, you would be wise to get the long drill bit. If not take the chance and line the holes from either side the best you can, drill them in as deep as possible from each side and hammer the livin' crap outta them. They might make through... I have been that fortunate doing it that way too. It does blow out the wood a little bit on one side. That is the trade off, if it works....
Best Answer
Knife with a sharp point. Dimple the surface with the point and gently twist your wrist. Turn the knife 180 degrees and continue till you've pierced the material. Do the same from the other side till the hole is the size you need. You have to be really gentle but it's a field technique I've used on up to 3/8" thick materials. Then go out and buy yourself a cordless drill so those bits become useful.
And for those who object. When the stuff hits the fan and you're 20 miles from home on your motorcycle, nothing's so useless as the drill motor and case of bits sitting on the workbench. Improvised field repair techniques aren't just for McGyver.