So if I return it and get another configuration, I may get a better or worse one depending on luck?
Yep. Just like Apple and every single brand of computer on the market. People have returned their MBP’s due to something minor and got a bigger problem in return. Like they thought one of the keys sounded a little different than the others and in exchange got one with a display issue.
You may get one that’s perfect, you may get one that has a more serious problem than the one you are sending back, you may find what you feel is a problem is just the way they all are. Up to you whether or not you take the chance, what you are willing to accept and how many exchanges you are willing to make.
Edit: My experience with 2018 MacBook Pros
Unit 1: Constant BridgeOS kernel panics, wavy/flawed screen lamination along the top edge. Returned
Unit 2: Arrived with sharp chips along the left hand side near the speaker. Returned.
Unit 3: Keyboard issues. Several keys not responding to input on first, second, sometimes 3rd press. Sticky 8 key. Temps and fans would run away for no apparent reason. Returned.
Unit 4: No problems whatsoever during the 14 days trial period, but decided I just couldn’t trust it for the long haul after the issues with the first 3. Returned.
Would the 4th one have stayed perfect and given me years of trouble free service? Maybe? Maybe not? I will never know
Edit 2: I sent back the original X1E, because Lenovo had a sale on them after I bought the first one at release. The second one it seems that the fans don't come on nearly as often as they did on the first, or maybe just not as loud. Maybe it is just because I don't have them both to compare side by side.
Also picked up a Surface Book 2 15" to compare side by side for a while to decide which way to go. For my needs, I am actually thinking about keeping the SB2 and returning the X1E. The 2-1 design suited me well with the Surface Pro and my wife likes my Surface Pro, so maybe I will hand that down to her and stick with the SB2