NZFF

Is there a manual for MSFS 2020 or where does one find an explaination for the setup options?

You will find a wealth of information and some useful guides over on the Microsoft Flight Simulator Forums otherwise recommend watching You Tube videos like these MSFS Premium Delux version after installation Tutorial Videos.

For a very through in-depth Tutorial explanation of the setup options highly recommend watching this recent uploaded video on the Australian Novawing24 You tube channel.

This is a best to date in-depth explanation of the setup, that I've seen so far. Note it's over an hour long.

However Novawing24 has time stamped sections click on the Show More description section, if you want to go straight to a relevant Time stamped section of the covering key points:

General Tab - 2:17
Graphics - 2:23
AI Traffic Models - 13:48
Camera - 16:40
Sound - 24:07
Traffic - 30:45
Airport Life - 33:49 (This one is going to be the biggest impact or I feel on your frame-rates / sim performance from my experience)
Data - 38:49
Setting up Off-line / Manual Cache - 42:21
Flight Model - 48:14
Miscellaneous - 49:05

Assistance Tab - 52:54
Piloting - 53:51
Aircraft Systems - 55:34
Failures & Damage - 58:03
Navigation Aids - 59:45
Notification - 1:02:26
User Experience - 1:03:21

Controls Tab - 1:03:59
Searching By Input - 1:05:12
Deleting an Input - 1:06:37
Search by Control name - 1:08:32
Binding Controls - 1:08:58
Profile Management - 1:10:53
Multi-command / Single input - 1:12:22
Keyboard and Modifiers - 1:14:08

Microsoft Flight Simulator Tips and Guides - Controls and Settings

Just what I was looking for.Thanks.