Okay, huuuge gear noob here lol.

I have a Behringer Ultrastack BG412V Cabinet. It runs at 200 Watts into 4 Ohms mono, or 2 x 100 Watts into 8 Ohms stereo.

I'm trying to choose a good amp head. I know I have to match the ohms, do I have to match the wattage too?

I was looking at this amp head:

Would this be a good fit? I'm trying to figure out something that would be loud enough for small-medium shows as well as general practice and recording.

Also, sorry if this is the wrong place to post this haha
Yes that will work with you cab. Your cab can handle up to 200 watts in mono which is the way you will most likely run your head. As for Ohms, you may just check Randalls website for that head to confirm what speaker out Ohm load is called for on those jacks, there are different mismatches that are ok, they don't have to be exact.

Look it up in the net....head, cab speaker impedance matching and you will see the different Ohm out (amp head) to speaker cab (ohm in) that will work.

As for wattage, as long as your cab can handle (in mono) more watts than the head produces you are fine.
Jackson: DKMG w/Zakk Wylde EMGs
Fender: Fat Strat HSS
Epiphone: Les Paul Custom w/SD Pickups
Dean: Performer E Acoustic/Electric
Vox: DA5
Vox JamVox
Digitech: GNX4 Workstation
Digitech: EX-7 Distortion Factory
Boss DR-880
MAudio Bx5a Deluxe