Here are some tips I found while using the army spawning tool

Removing Spawned Armies
Armies spawned by this cheat menu are classified as special soldiers[ck3.paradoxwikis.com]. Unfortunately, there isn't any button you can press to delete special soldiers. PDX-Unlimiter can be used to decrease the number of soldiers, but doing so disables achievements for your save files.

The quickest way I found to get rid of these spawned soldiers is to send them into battle without a commander. Doing so will get them killed much quicker, even if they consist of a bunch of MAA. Of course, your spawned army may instead go on a shattered retreat after a defeat instead of just fighting to the last men, but you can use this no retreat mod to quicken their deaths.

Spawning MAA
By default, spawned armies consist exclusively of levies. However, you can edit spawned armies by going to common/decisions/003_daddy_pikas_decisions.txt (h/t this thread.

Suppose you want to spawn an army consisting of MAA. To do that, add the following block of code inside 003_daddy_pikas_decisions.txt (I personally added it after the army_spawner_3 block, but I'm not sure if that really matters):


The code above will add a 4th button that, when clicked, will spawn 10 Armored Footmen stacks (1000 men), 10 schiltron stacks (1000 men), 10 Light Footmen stacks (1000 men), 5 Longbowmen stacks (500 men), 10 Armored Horsemen stacks (500 men) and 5 Bombard stacks (50 bombards).

A list of all Men At Arms types can be found inside game\common\men_at_arms_types