When I sail and just fight normal ships it's mostly fine with my Frigate, however near end-game and Swamps.. most enemy ships are also larger Warships and Frigates.
This takes my FPS from a comfortable 90-100 to 40, sometimes almost 30 during the massive "0/20" boarding battles. There's a lot of jankiness going on with this and makes the high level ship battles a bit unplayable / unenjoyable currently.
See attached screenshot - 38 FPS boarding the Stede Bonnet fleet and fighting it. As soon as I sunk it the FPS recovered. 50-60FPS recovered the moment I left the boarding.
Playing on a 5700X3D, 32GB RAM and 9070XT.