Regarding the apparent higher power of clan weapons, it's not as bad as it seems:
Clan equipment tend to be lighter and smaller than IS, so they can usually pack more on. But their lasers are far less heat efficient than IS lasers, and tend to have pretty long durations. Their ACs fire 3 shells instead of 1, meaning the damage tends to get spread a bit. Their missiles are the same as the IS ones, except for some reason Streak SRMS, which get a little extra range for no explicable reason.
So clan tends to have a good advantage at long range. All else being equal they will win the poking game if they're allowed to fire at their leisure and cool off.
Where clan does not have the advantage is brawling. If you can push against a bunch of clanners, they will get off impressive alpha strikes, but then their DPS takes a dive as their less heat efficient weapons need more time to cool. Their long duration lasers and spread out ac shots mean you can twist the damage pretty well, while the short duration IS lasers and single shot ACs are a lot easier to keep focused.
The dakka kodiak 3 is a special case. The UACs do fire 3 shells per attack, but they're pretty heat efficient. Kodiak 3s are seemingly pretty OP, but they do tend to get focused down because of that.