This guide has some basics. There are a lot of subtle and handy bits of UI in Total Warhammer, so I would suggest revisiting tips and videos between plays and trying elements you are unfamiliar with. I listed some good video channels here.
In the control options, there is an advanced tab that lists stuff like alt+click to drag selected units in relative formation (alt+ctrl+click to rotate), or alt+rightclick+drag to position and aim a ranged unit. Holding spacebar shows unit orders and opens a side-panel that lets you toggle visual bits, like hiding nearby trees so you can see units better. I always play with the detailed unit stats panel open (I key), and classic battle camera.
I don’t use locked control groups much anymore (alt+click to drag big selections is just faster to set up and won’t ruin your hotkeys), but they can be good for engaging a long front line all at once (the units will march in line, then pick targets and charge, which is better than just mass-moving them, and less work than targeting them one by one). You can also re-arrange unit cards (in battle only) and then shift-select and drag-place to make a line in that arranged order. Control+click to select them in a specific order and then drag-place is supposed to work similarly, but maybe it fails for some unit types or is just unreliable.
To overcast spells (extra effect, +miscast chance), you double-click the selection icon before targeting. I don’t recall if this is always available in TWW1, but repeated clicks will cycle through cast/overcast/cancel. In TWW2 overcast is often a per-spell upgrade/unlock. IIRC, you always have it in TWW1, but upgrading decreases the miscast chance.
I made this mod list of quality of life stuff on the workshop. I used to use “less op agents” and “home region movement bonus” too, but game updates have improved balance/AI and made them unnecessary.