You can have better traction and comfort from using the shock or you can have better efficiency and speed from not having it absorb some of your pedaling force, but you can't have both at the same time.

There's a reason the only bikes you'll find with suspension are MTBs, hybrids marketed to newbies who don't know any better (sorry), and high-end e-cargo bikes that have excess power budget to spend on jostling the cargo less.

Also, keep in mind that your arms and legs (if you stand up on the pedals) act as shock absorbers, even if the bike itself is rigid. The tires and even the frame flex a little bit, too, and that's basically considered good enough on paved surfaces up to and including cobblestone streets.

Well the good news is that if you ride this guy for a while, and then do decide it is overly limiting for you, getting on a road or gravel bike will be a big instant speed boost.

Definitely get in good with a local bike shop now, and have them do maintenance on this bike. They might end up giving you a good deal on a trade if you do decide you want something else, but they will usually only do that for established customers.

The tour de France is very mountainous. 50 is 30 mph here and I averaged up sure. I'd bike with pros on the weekends and they would blow by me. But the space between lights were a sprint and I would overtake traffic each time.