We're using a test account that loads horrendously slow compared to other test/production accounts(can be about 10 seconds of waiting), whether it's opening entity records or saving new transactions. How do I go about finding the source of the slowdown and fixing it as an Admin?

Have you tried reviewing the APM data? That will usually tell all.

Yes someone directed me to it too. I'm having difficulties understanding it though it's abit overwhelming as a non technical. Any tips?