Well, I'm one who has several custom installs of Orbx that are not in the P3Dv3 root folder and I must say, FTX Central v3 has been exasperating to say the least.
1) FTX Central v3 and OrbxDirect are centrally tied to the registry now and will be from here on out.
2) No matter what sim you're currently running, if your install of Orbx is fully stable, transferring your FSS licenses to OrbxDirect will not affect your current install in any manner.
2.1) Updating any of the scenery files or library through FTX Central v3 has screwed around the scenery.cfg file order. This is a known bug and is being addressed. Sadly, customers have registered new complaints regarding the latest FTX Central v3 update of itself.
3) After transferring your FSS licenses, you don't have to re-download anything or reinstall anything for your current Orbx scenery to work. It will be simply activated when logging into FTX Central v3.
4) Since Orbx has requested and FSS has agreed, the current FSS wrappers will continue to work should the need to reinstall due to HDD or SSD catastrophic failure. This will aid those who have to reinstall OS, Sim and Orbx from scratch.
5) At some point in the future, when all the "box of rocks" have quit their panic downloads and bandwidth has once again returned to normal, backup downloads will be much quicker than before.
Orbx could have and should have presented the necessary procedure more clearly in a logical and business like manner: NO EXCUSE.
I would (did):
a) Setup an OrbxDirect account;
b) Transfer FSS licensces;
c) Install FTX Central v3;
c.1) Migrate and activate the scenery;
d) Do not update and scenery files, the library or FTX Central v3 itself at this time.
* Note for c.1): Since I've got several custom installs and am running Orbx on different drive, my scenry.cfg files were completely altered. I simply used my cfg backups and all was well. I don't think this would happen to a default install, but I'd backup my cfg just in case.
Just don't update anything as noted in d).