I have these exact boots and they're great. The lacing system works well. They're easy to get in and out of, unlike some other winter shoes. For reference, mine are size 43 and I wear 8.5 US in most shoes.
Seating one side definitely helps. You don't have to use a tube in most cases, just push it in place while the other side is off the rim. Then when mounting the loose side, take your time and try to get the bead as close to the rim as possible. Then, while blowing air, nudge and massage the...
I ride a 2018 Hakka. I have 2 wheelsets - 650 x 45 with some knobbage (Pirelli), and 700 x 32 Gravelking slicks. The Hakka is a bit twitchy to me, but it's designed to do CX if you want to. I vote for stability over quick handling if you're gonna ride primarily gravel. Loose gravel over hard...