Traktor and rekordbox, flac and mp3/AAC

Hey everyone.
I have a concern/question and some of you can maybe have suggestions.
So I have my collection in FLAC that I use in traktor.
But I also use sometime my xdj-1000 directly without traktor or some cdj that does not support FLAC. So for now I also have a duplicate collection in AAC that I use in rekordbox, not ideal.
So few things:

I can have only one collection in Mp3/AAC but I'm always worried about the quality compare to FLAC for example. As everyone I read lot of different opinions, but will be happy to have yours about FLAC vs Mp3/AAC, wich one should/could I use?

Other thing is, I mainly use my Flac library in traktor, so tagging tracks etc. I'm fine with having a duplicate librabry, but one thing is how to transfer the tags I have on the FLAC files to the converted AAC files? (that is also a concern if I decide to switch and use only one library of AAC files, how to transfer the tags from the Flac files).

Happy to hear any ideas.
Thanks

You can copy Traktor tags manually by using a id3 tag manager (copy/paste entire id3 tag).
It's good that you care about sound quality. But be assured - your audience doesn't/is unable to. You will loose nothing by just downloading FLAC, making a mp3 copy to put through Traktor and making a FLAC archive to use later when it/if becomes a generally accepted DJ format.

Thanks for the advice. And yeah I decided to convert everything and use only one mp3 library, and keep the flac files in backup.
I made some search and as you say I saw taht I can use a tag manager software to transfer the tags. But I made a little test yesterday and something weird happen, and not sure how this is possible.
I made a test with one track, so a flac file that I use in traktor, and I guess key, bpm, star rate, comments etc all these are tags attached to the file right? (if you ask to be attacehd to the file for sure). So I converted the track in mp3, tell traktor the location of the mp3 and strangly traktor recognize it as the previous file or so, keeping the tags etc. And I'm also wondering if traktor does also rewrite the tags on the new mp3 file. Is that possible? If it is it's amazing.
Or does the conversion also keep the tags and attached them to the new mp3 file?

That depends on the software you use.

OK I see