There are free 15 minute treatments at A and B - you can book them in advance but the email address for the spas inside the lounges I have lost, but you might be able to get in touch via the website: https://www.timelessspa.co/ - you can combine them with a paid treatment if you want more time or a combination of programs. Much will of course depend on how much time you have before boarding.

However, I don't really think that reservations are required for around 1pm local time.

Basically, A has the best showers (and I guess a cigar lounge if that's your thing), B the best dining facility (even though A and B are quite similar) and C has the best wine. There are two F lounges in C, but one of them is a combined J/F lounge so you wouldn't go there (and it's right at the far end of C). If you are departing from A, note that the internal gates at A open very late (sometimes after the final call time on your boarding pass): that's normal, don't panic. Sometimes though they will open quite early (that's often the sign of a bus gate - but F has its own bus which is more like a big luxury minivan).

There probably isn't any point doing a lounge trip as the distances can be quite significant (10s of minutes of walking and it may be quite warm) - just go to the one in the concourse of your departing flight.