A couple suggestions if I may:
1.will power washing be good or should we acid wash the brick. there was a hot tub on parts of the patio so there is some color differences on the patio
Acids can be harmful to surrounding plants so if you decide to use it be very careful. Also, you can etch the surface if the acid is too strong, so again, be very careful.
2.Any recommendations on sealers and how to apply.
If you plan to stabilize joint sand and seal the surface, try using a product that will do both and save yourself a lot of time! Recommend: Surebond Joint Stabilizing Sealer (available in matte and gloss finish)
Hope this helps!