Are there any side quests in Dawnguard and if so are they any good? Or is there just the main Dawnguard/Vampire Quest?

there are plenty, talk to the peple in the castle / fort, and there are new locations as well, books also will give you new quests, there is enough to keep you busy for a bit. I enjoyed them all. still not done, but then again, i never fast travel.

They are never ending radiant quests
However they added a dwarven ruin quest
Many small quests in the soul cairn
Unlimited dawnguard/vampire side quests (the vampire quests can be very buggy and can glitch fatally)

According to memory you had quests such as this:

SPOILER ALERT FOR MINI QUESTS!!!



Kill a vampire masked as a bard, merch, homosixual, or escort.

Clear out hollow areas of vampires such as george bushes skull, caves, cabins, etc.

Collect dwarven plans from bandit caves, cabins, etc or you must intimidate the cast of little people big world for the plans.

Recruit

repeat. Those are the only things that come to mind atm.

And vampire alternatives

Homosixual? Uhm..

There are but in my game the just refuse to start