Ophie
Salingerian Phony
So the only difference is the level and that they have a different number of max IVs?
No difference in likelihood of HA, egg moves etc or different rewards between a 1 star red raid and a 5 star yellow raid?
If it's the same species and draws from the same pool, it'll have a higher number of guaranteed maximum IVs, be at a higher level, and have a higher range of possible Dynamax levels. Everything else is the same.
If it's a Gigantamax den based on an event (currently, that'd be Drednaw, Centiskorch, Sandaconda, Corviknight, Butterfree, and Snorlax), the level will be higher, there is one more guaranteed maximum IV, and the Dynamax level range is higher too.
The same location will draw from a different pool depending on if it's the regular beam or the powerful beam. The regular beam is the common den; the powerful beam is the rare den. In most such cases, they have a lot of Pokémon in common but not all of them, and the rare dens have a larger list of possible Hidden Abilities (and a higher likelihood they'll have them). For instance, a den in Hammerlocke Hills spawns Ice-type Pokémon. The common den is Den 23, and the rare one is Den 73. Both dens allow for a Froslass with a Hidden Ability (Cursed Body). However, only in Den 73 can you find Mr. Rime with a Hidden Ability (Ice Body). Inversely, only in Den 23 can you found Frosmoth with a Hidden Ability (Ice Scales). The other den has the Pokémon, but it's always the regular Ability. Den 73 contains Glaceon, while Den 23 contains, depending on the version, either Eiscue or Darmanitan.