The main difference I noticed was grin being considered fairly weak for privacy as it hides historic information and transaction amounts but those can be gathered before a transaction is confirmed
This is quite wrong. An accurate overview of what Grin and Monero hide can be found at
https://forum.grin.mw/t/scalability-vs-privacy-chartwhich also shows how scalable various blockchains are.
Is coinswaps available on grin now then (I just realised how old that link was too but it was the first result I got).
Without MWCS you can see addresses that get paid in the mempool, with MWCS (if it's implemented) you wouldn't be able to trace anything from what I can tell as long as mixing is done frequently enough which it would if it scaled to bitcoin's size.