I can’t say much about Titanium Backup, as I never used it … if it’s any good, it should work that way I guess.
Be safe with a backup …
… substitute my usage of MyPhoneExplorer with your usage of Titanium Backup (if it is able to completely backup Internal Storage), and you should be good to go back to the LineageOS installation which worked before, if all else fails.
microG tries to mimick Google services as good as it can, so in an ideal scenario the Apps themselves shouldn’t notice and work just fine.
Possible problems might arise from the fact that you can’t 100% rely on microG.
Google services constantly get updated and changed, so that microG constantly has some catching up to do. In the meantime Google-dependent Apps might become a pain to use (before the last update e.g. Discord nagged me about having to update my Google Play services every single time I tapped something in it, not only when I started the App) or downright break.
If you really are dependent on these Apps to work, you should consider staying with GApps.
If it’s just a nice bonus for you to have those Apps perhaps working, and you could otherwise live without them or use a website version of them in the browser for a while, using microG should be fine.