My understanding is if you get TPS with EAD, your current TPS status will be active and H1 on hold, so that you work under EAD not H1B. If you apply for Advance Parole, you can travel to Nepal for a short period of time with valid reasons. Once 18 months of TPS is completed (if not extended), then if your H1B is still valid, you are back on same old H1B status. As far as H1B layoff is concerned, you have 60 days (not sure) to get another job and transfer H1B.

So, think wise what do you want ?