I know this issue has been covered several times, but only with opinions from people. This is a summary for everyone who is on H1b and have applied for TPS.

1) What happens when TPS program ends? Do you easily go back to H1b? or do you have to reapply for h1b? are you subject to cap?

2) in order to avoid "out of status" periods between finding jobs should you have to quit your current job on h1b, is it better to apply for TPS with EAD or not?

1. Your status ends with TPS end
You can go back to H1b after reapply only
Whether you are cap subject or exempt depends on your prior H1b type and duration
ie if you had H1b on cap subject status, you will have total of 6 yrs of cap exempt H1b!

2, If you have H1b now, keep working on H1b, no need to quit the job , and start applying for TPS;it will be cancelled only if your TPS is approved. If your TPS is denied, your H1b will continue if it's expiry date continues to be valid

If you do not have H1b now, just apply for TPS, you will get Work Permit in about a month or hopefully sooner.

This is a usual H1b common sense. Confirm with lawyers if see if there is new update or if you have serious doubts .

"it will be cancelled only if your TPS is approved"

This is wrong information. Approval of TPS will not cancel any other status. It goes parallel with any other status. H1 will be revoked or cancelled only if you leave your job and your employer revokes it.

the only reason I want to apply for TPS is that in case I might have to quit my job one day, I won't be out of status the other day (or so I've heard)

Getting approved for TPS does not affect H1b in any way. If TPS EAD is used for employment in place of h1b, then H1b is affected. So putting TPS as a back up plan while on h1b is always good.

by "Don't use TPS EAD", do you mean I can apply for EAD while on TPS but just keep in in my drawer, or just apply for TPS without EAD?