In high-transaction environments like yours, it may be necessary to supplement this with manual vacuuming.
Few Recommendations
Monitor Long-Running Queries try to optimize. Optimize Autovacuum. Partitioning. Adopt Vacuum Strategy after peak hours.
We have these big tables already partitioned. So does "vacuum table_name" will endup scanning whole table or just the latest/live partition which is getting loaded currently? and do you mean to say running command "vacuum table_name;" frequently on selective tables that are experiencing heavy DML ? Hope this won't lock the table anyway because the data will be written/read from these tables 24/7.
When you say, "optimize autovacuum" does it mean to set a higher value of "autovacuum_max_workers" and "autovacuum_freeze_max_age"?
Considering we have ~4 billion rows inserted daily into the table and there is limit of ~2billion to the "Maximumusedtxnids", what threshold should we set for the alerting and to have enough time at hand to fix this issue?