I have played a few of the games in the Might and Magic series, and am psyched to try out MMVI - is there much in the way of level/experience grinding in the game? Are there any suggestions about making a powerful party?

Experience in M&MVI is not a problem. Plenty of Enemies.
I find Druids the most powerful early to mid-game. Sorcerers Late Game
Others will tell you to get bows. I don't see it that way. They are convenient but early, simple spells work better (Not, Magic Arrow or Flame Arrow which are no better than Bows. Harm, Sparks, ice bolt. They are good early spells. And Swarm and Sparks stay good to mid game.)
My favorite Party: K/D/C/S
The only actual grind would come mid-game, but I never felt the game lacked experience just staying alive.
Edit:
There is a mini-grind. Castle Ironfist. M&M VI and the Sunday Arena from Ironfist. But also an in-map arena. In that arena, enemies will come in waves for a while. But after about six times, it stops until the map itself replenishes which at Ironfist is two years (maybe). You access the in-map arena from a teleport in front of the Castle's Main building.

You can grind if you want. Or just run and grab what you need for the quests. Some quests require defeating a foe, but many others do not. The promotion quests give lots of experience and some are simply running to a spot and then running back to the quest giver, once you know what to do. Teleporting magic is really helpful for such an approach, just run there and then teleport back.

No need to kill everything. Many foes are rather realistic in that they will run away when hurt too badly, so it's possible to keep healthy after they start to run away and carry on. No experience for not defeating them, but no further loss in health either, so exploring can be quicker. Though some foes will fight to the death, so maybe avoid those.

Get a notebook, or a create a new file on the computer, and keep notes of everything. Makes playing through again more personalized than reading other people's notes and walkthroughs. Play more than one game at a time, no need to finish it before starting another. I've found it helpful when maybe I didn't write down all the detials of the quest, and the Quest Log is sometimes scanty in important details. Starting a new game to get the quest again helps with that, and in that case just running to get the quest without bothering to fight can be much quicker. Might and Magic VI allows saving dozens of games.

Gavindale, did you notice the earlier thread, "Is it just me or is MM VI the most stressful of the later series?"

Most dungeons and maps repopulate after 2 years in-game time (the passage of time does matter a bit). That is more time than needed to finish the game. A few repopulate in 6 or 8 months and we might revisit one or two of those, but the mobs then will be easy to brush aside and not worth hunting down.

There are plenty of areas where killing all hostiles takes a long time (our time as players, not just in-world time) and at the end we have achieved something. If you call that grinding, then MM VI is a grindy game. But we don't need to keep repeating the same repopulated areas just for more experience. If we come up against foes that are too much for us -which you will, first time through, not knowing what is where - the answer is to go somewhere else not yet visited. Maps are designed with mixtures of mobs and dungeons of different levels and we are meant to do what we can, coming back for the rest later, maybe much later. (As is typical of Might & Magic games?) Just because we have been given a quest, that does not mean we are ready for it - other than by run in, grab and run out, as already mentioned.

Some quests, including some of the main-storyline-compulsory ones, do require us to fetch something we can get (or get the key for) only by killing the boss.

My own take on party composition is that even if not the most powerful, the default party (P/A/C/S) is the safest, and anyway is what the developers have challenged us to use.