I didn't mean to put you off about the OPD on the 20lb tank...it's just something that everyone who uses a larger tank needs to be aware of. I've tripped the OPD on my larger Genesis grills, because I tend to crank down tight on the tank valve which makes it harder for me to open the valve slowly. To reset the OPD, you simply just shut everything off and let it sit for a short while and then retry, remembering to open the tank valve slowly. An indication that the OPD has tripped is that the grill won't heat up beyond a certain point, usually about 300F for me. A tripped OPD is less likely to happen if the regulator is right at the tank, but it still happens under the right conditions. I don't recommend that you change out a brand new OEM regulator because of a potential OPD problem, just be aware of the issue and work accordingly.
If portability is a factor, note that none of the Q series is truly portable in that it takes two hands to carry one, and another hand to carry the stand (the grill is intended to be removed from the stand for transport). The fold-up stand is considered by some to be rickety, although I personally don't have a problem with it. On the plus side of things, the Q1xxx will run nearly 3 hrs. on a 1lb. can of gas, the Q2xxx almost 2. Some people refill the disposable 1lb cans, which can be finicky to fill completely, or there are refillable cans available. I think the Q1xxx and Q2xxx were designed to be mostly stationary with occasional portable use and they suit that purpose well.