I know they affect smacking with shields and two handed weapons, but do they affect the smacking damage with bows?

Found it to be quite useful up close, smacking the enemy, going into slow time and then shooting them in the face.

The blocking perks have some of the best i've saw so far,like block 50% of all magic damage you recive or these you mentioned.

Yes. Bow bashing damage is increased by the Block perk. It affects all bashing, not just from shields.

Yeah thats only for shields though, I'm talking about the perks that 5x the smash damage etc.

The Shield perks in the Block tree are nice. The drawback, though, is that you have to use a shield to get them. Yeck!

I've mastered sneak, illusion and conjuration on my assassin character, just playing about with shields. Using a glass shield and a glass dagger, both have 2 enchantments. Daggers with paralyse 1 second wreck any enemy if you can get close enough ha. But until the magic resist is fixed I won't be able to kill mages unless its stealth.

Just testing it out, had a few perks to spare, so I brought the power bash and 5x bash perk and the bow smash damage didn't seem to do any extra damage, nor could you power bash.
It does affect 1h weapons and 2h though, does anyone use the 100 block perk, run with the shield up knocking them down?

I use it. It's pretty solid and a lot of fun when you knock people down stairs, off cliffs, ledges, etc.