Rare released performance improvements in patch 1.0.2 and now they are at it again, patch 1.0.4 will bring optimization improvements across the board.
In this patch Rare will be fixing quite a lot of problems that Sea of Thieves was facing, these problems include: rain appearing in the Legend Hideout Tunnel, text bugs in the Reputation menu UI and ships unfortunately spawning with damage already taken.
Rare will also be adding performance and stability improvements in this patch, more specifically "Improved performance on high resolution PCs running at lower than native resolution." Rare has also added a "Increased quality of island rendering at a distance when using the spyglass on all quality settings on both platforms." Rare also addresses that there will be "Further improvements and optimisations for all platforms are ongoing." There is much more that has come with this patch so if you are interested in reading the full patch notes visit the official Sea of Thieves website patch notes post here.