I'm sure LCW will look more impressive, but that's mostly due to his extremly low body fat content, not the size of his muscles. If you were to increase LCW's BFC to the same level as an NFL player of similar height and put them next to each other he'd look like a starving kid, for example....
I haven't seen a single picture of Mark with his shirt off so I can't say for sure, but with the shirt on he looks to be at least as wide as LCW. He's 14cm taller - that's a huge height difference. LCW probably still had more muscular legs at the end of his career (and definitely in the 2006-2012 era), but his upper body is nothing to write home about
regarding pure muscle mass. The impressive part was always his extremly low BFC, most other players wouldn't be able to keep it that low consistently and still perform/keep their muscle mass stable.
I'm sure part of why you find his smash so impressive is also that it's mixed, the defenses are a lot spottier than in MD. He also seems to have very good choices on attack, rarely smashing all out when he's not in a good position, often waiting for a slightly short lift before really turning up the heat. I watched some of his MD with Marvin Seidel and the smash really didn't blow you away there, better lifts and stronger defenses, I guess.
Also, LJH definitely has at least comparable smash speeds, if you don't find his smash impressive that's mostly your perspective. LJH is consistently one of the hardest smashers on the tour, I'll agree that he doesn't make the most of it sometimes and loses the angle. Goh VS is probably a good analogy for Lamsfuss, similarly unassuming physique but a very effective smash. I'm always a bit surprised when GVS smashes, he's also fairly thin and compared to other hard smashers tends to not rotate his upper body that much. I really wish I had a rotator cuff and shoulder like that