Indeed, the difficulty's higher than that of Fo4. In several hours playing this game, the number of times my character has died in FoLon is very much higher than that in Fo4... or Fo1/2/3/NV, for that matter.
I think that in Fo4, it's easy to rely on / get spoiled by the various protective properties of the T-45 Power Armor found at a very early stage. I'm certainly not the one who did. Leveraging that Power Armor set isn't mandatory, but not taking advantage of it is akin to gluttony for punishment... I never looked back to non-Power Armor types after that, though underneath the successive Power Armors, wearing armor parts with special LK/CH/AP/etc. effects brings various nice bonuses.
So far, I'm not yet feeling a change in the approach to playing the game, though. This game still feels very much like Fo4. In order to help avoid sources of radiation, I can draw from my Fo3 and Fo4 experience (well, FoNV as well, but there's less radiation overall in there). Sneaking around and avoiding wildlife when possible remains a good idea to spare ammo.
Playing Fo4 has definitely modified my style for a new run of Fo3 I started several weeks ago: lower usage of VATS, higher weapon diversity, higher proportion of close-range fights though they hurt more than on Fo4 because even Power Armor sets, which I'm not about to get in Fo3 because I'm going through most of the map (in order to pick up books and quests) before progressing the main questline, is far from being as protective as on Fo4.