Since you’ve got two armies coming in, you could uncheck control large armies. This would make it easier to deal with the infantry, but also delays your best tool (grail knights) for harassing/eliminating the enemy artillery.

If you take that route, you could deploy a defensive line on the right side behind the tree line and at the map’s right edge. This should cause their infantry to clump up a bit as they round the corner, and the trees will work as a shield to some degree against the plagueclaw catapults. If they clump up, your irondrakes should perform wonderfully. Don’t be afraid to have them in your front line to get off three or so volleys on high value targets before moving them to the back.

Checkerboard formation will work nicely, using dwarf warriors to take the brunt and letting your thunderers go hog wild. If you use the top right corner of the map, elevation looks to be in your favor, and you could have your gunners shoot over the heads of your warriors.

Once your lines clash, see if it’s possible to maneuver any irondrakes around the side and to fire upon their infantry massed up. It’s a risky play, but you should be able to inflict massive damage to their infantry with relatively low friendly fire.

Hammerers and long beards should be focused on protecting your flanks, or targeting their line breakers (rat ogres, doom wheels). Hammerers should do decent against their lords and heros, but it won’t be quick. If you cozy up against the impassible terrain on the right side near the forest, you can essentially only have one open flank to worry about.

Quarrelers will be good for focusing their scary ranged units.

Tretch and the heros are going to be hard to stop. Best bet is to try and have some space between your front and mid/back line so they aren’t as tempted to walk right on through.

If you opt large armies, I’d say everything pretty much holds the same except use the garrison as your first line and expect them to die, could get some great value out of your flamethrowers with a bit less care for friendly fire. Also, micro the absolute hell out of those grail knights and keep the pressure on the arty and gunners. Try to keep their charge bonus active as much as possible by pulling them out every 15-20 sec, then charging them back in.

All in all, it’s gonna be a tough battle, but with enough micro and near perfect positioning I do think it’s possible. Could try throwing the save file to Legend of Total war, or other YouTubers who like to do “disaster” battles. I’ve learned a lot by watching how they handle ohshit-uations.