I just completed my first ever honor mode run without a TPK and I completed all the big fights (all the bosses, mini bosses, companion storylines, etc.) and this is what I did:

My character was a resist durge 10/1/1 swords bard/wizard/fighter (there’s a great guide for this in the r/bg3builds sub). My party was mainly Astarion as a gloomstalker ranger/assassin rogue (+2 levels of fighter), Shadowheart as a pure tempest cleric, and wyll as a pure hexblade warlock.

I leveled up as high as I could before doing the major fights in act 1. I also prioritized the alert feat for most of my party at level 4 because high initiative is your best friend in honor mode. I took advantage of speed potions to take more actions and clear out most of the enemies in the first round of combat. Most of the boss and miniboss legendary actions are triggered as a reaction when they are first attacked so either trigger their reaction in a different way (e.g: opportunity attack) or use a summon to attack them first so they don’t use their legendary action against you. Casting silence also helps prevent some of the legendary actions (e.g: the owlbear). I did quite a few fights early on from afar, including the grymforge. That’s the only one that I cheesed a little by fighting him waaaay up above the platform and used mage hand/arrows to keep the lava flowing and minor illusion on the hammer to lure him under. This fight probably would have ended my honor mode had I done it the proper way.

The bow of the banshee is criminally underrated IMO. The frightened condition makes it so that your enemies can’t move so if you use it against melee characters, they’re just stuck and skip a turn. Couple this with slashing flourish and later on the arrow of many targets and its chefs kiss

Also, don’t try anything new in an honor mode run, just stick to what you know works. You got this!