For the first one, I recommend Nucleus, it’s a huge multi purpose essentials plugin. It has kits, one of which you can set to the “first time kit” so that new players will spawn with specific items. Specific documentation on that here, but there’s a whole section of documentation
As for the second, I don’t really know Pixelmon well, so I can’t help you there, but maybe someone else will know.
Pokeheal is a default Pixelmon command, I thought. If not, then it’s part of a Pixelmon sidemod called Pixelmon Extras or PixelExtras. You can use a permissions plugin like LuckPerms to make a group for all players to be put in automatically and also set it to give them the permission nodes to use practically any command you like them to have access to (/tp, /pc, and /pokeheal included).
All mod commands are in the format <modid>.command.<command name>
So your example of pokeheal would be pixelmon.command.pokeheal, you can find all the command permissions on the Pixelmon wiki page for commands here: https://pixelmonmod.com/wiki/index.php?title=Commands