Recent system issues makes me want to isolate my p2p environment.

My objective is to use a large USB drive to contain all my p2p apps, configs, metadata, links and files.

I have never used the portable versions, but it looks like the way to go and that it will create a p2p system that will work on either windows or linux, depending on what is available to me. I like that idea of plug and play.

I would like to migrate my existing tixati environment, which on one system has about 500 torrents. Once I get the new ext HD prepped with the portable versions of all 3 apps, what is the best way to migrate the content folders and the config files?

Since fopnu and darkMX are simply links to the share folders, those are not a big issue unless I am over looking something. It is moving the torrent content files, and incomplete files over and the related tixati list of transfers I want to get right.

All hints and advice welcome.

For encryption I think Truecrypt/Veracrypt is still the only cross-platform and trusted solution. Before you start filling your drive with data, encrypt it. Saves you the headache of clowns in masks snooping in your data. With Veracrypt and high enough rounds of password encryption even a weakish password should do.

In contrary I've never used Tixati installed versions, I think the only difference is that portable has a text file to show Tixati to start in portable mode + config files in the same folder.

Migration of files: Tixati is excellent. I've moved probably terabytes (total) by now just using the built in system. I remember ~5 years ago uTorrent was barely capable of doing that task.
Tixati can move files around without freezing or stopping the transfers. They continue as usual while the move happens in background. You just need to apply the new download/seeding location.
uTorrent completely halted transfers and partially froze if I remember correctly.

I haven't tested live Windows-Linux migration yet, there's only one forum thread so far that said they created symlinks in Linux root to the old drive partitions. e.g. /c/ -> /mnt/anotherDrive/oldPath/ for the old "C:" Windows drive.
In case of Tixati being on the same drive as the download folder, it picked it up automatically across Windows/Linux (relative path instead of an absolute path? e.g. "../downloadFolder/" rather than "C:/downloadFolder/"

In conclusion, there's not much to consider and not much work to do. It appears really flawless, just that drive path thing to confirm.

I'm confused as to how this would work.

I know I could add the drive, then have the installed tixati move files to it.

But after that, I would be using the portable tixati installed on the ext HD.

So it would need all the metadata files and configuration. But wouldn't the path on the system installed tixati be different than the path from the portable tixati location since I assume it would be relative?

It doesn't matter what your installed Tixati does and where it is with portable mode. Portable mode saves all settings in its own folder and registers/unregisters .torrent and magnet-link file open associations on startup (and you can set to revert it on exit). Once you've done it: you'll only start the "portable mode" .exe file.
One more thing: don't forget to move the incomplete pieces folder if you wish.

Here's a directory listing for portable mode (all the files it needs must be present in the same folder as .exe)
Note I've excluded "lastloadok" files

Step 1: you don't need to redownload Tixati, just create an empty file "tixati_portable_mode.txt" where you want to have its data
Step 2: Move .exe to that folder
Step 3: Move dat files there
Done

You can test it now with any folder and it will continue where it left off. Once you have the HDD, move this new Tixati folder there and then start managing file locations
PS: The big USB3 HDDs by WD/Seagate are the same as internal HDDs but cheaper. The WD HDDs specifically are the rebranded server HDDs on helium. You can extract them from their enclosure "shucking" and use them normally in your PC (you may need to cover (isolate) the 3.3V pin physically on the SATA power connector as it controls power up/down and defaults to down)