When transitioning out, can you use TA for an online course and the GI Bill for an in-person course at the same time?

You can use TA up until you separate, assuming you're not flagged or otherwise ineligible for retention. Your class date can't carry you past ETS. You can use your GI Bill any time you want you just won't receive BAH until after you ETS.

So you want to use TA and the GI bill at the same time?

When do you ETS/EAS? TA eligibility can time out if you are near your exit date.

I would exhaust all other resources like TA and yellow ribbon before tapping into your GI bill considering all of the other benefits tied to it