I’m not seeing the similarities. Watching the players play helps.
Also, if you look there's a clear regression trend in Johnsson now over a five year period after one good season. The problem is when you sign a UFA, fans assign a bias to some degree and expect player to not just meet the value, but exceed it, and do so consistently within seasons and Year over Year over entire life of contract.
Palat's had some streakiness on goal scoring, but his overall peripherals and metrics are quite excellent and hold up even when broken down between various linemates when he was moved up and down in the lineup. Cooper moved Palat up and down based on needs and matchups. He kind of was a swiss army knife at forward. I think Lightning are hoping that Nick Paul can take what he showed in playoffs and kind of provide the kind of consistency and impact Palat had with so many linemates, but remains to be seen, and I think Paul is still more of a 3rd/4th line guy.
I watched Johnsson enough to know, while he he's a smart guy who plays positionally and coaches trust him even when he can't score to save his life, he's not particularly useful given he is not physical, his board play is weak, and he's not the best puckhandler/passer. Palat may not excel in a particular area, but he generally does these things well and thus is a better well rounded and I firmly believe will be a more impactful forward.