[skyomish]

By now I have my installs so.
1. v4.08+UI1.1+additional mods (was too lazy to install 1.2) with version switcher for playing online 4.08, or offline 4.09beta modded.
2. v4.09 unmodded.

If I install HSFX over the 4.09 Version, is it possible to switch back to the unmodded 4.09 as easy as with the other version? What would you recommend?

I have to ASK what 4.09 are you asking ABOUT?
If its 4.09b1m the answer is NO - this only works with the UI 1.1 or 1.2.
If you are asking about HSFX-V4 the answer is yes with 4.09m.
Install goes like this disk 4.07m-->4.08m--->4.09m---> HSFX-V4.
With it you can turn the mods on and off - back to the ORG. 4.09m game