I use the 3Doodler Create+ (https://the3doodler.com/collections/create-pens) with my Mini2, mostly because I can use exactly the same filament (2.85mm) as what I am using for the 3D print itself. I use it for modifications to prints, and, as you say, welding where needed. Speeds are limited to 2 - “fast” and “slow” but they seem to work fine. The PLA setting on the 3Doodler works fine for my favorite Mini2 filament, ColorFabb’s nGen (see note at bottom for making filament sticks).
I believe the default nozzle is about 1mm, but I also have an accessory nozzle kit (https://the3doodler.com/collections/create-accessories/products/nozzle-set), which has several nozzles down to 0.5mm (round). Different nozzle shapes are also included, and a smoother tip allows adjustments to the surface.
Note that because the pen’s feeder rotates the filament, the filament strand must be pretty straight, like the supplied filament sticks. However, I make my own sticks from whatever Mini filament I am using. I cut a strand of (curved) filament from the roll, then insert it into a straight aluminum tube with an inside diameter close to the filament’s OD (aluminum tubes available at hobby supply stores). Then I heat the tube/filament gently on all sides for a minute or so with a heat gun, medium heat. I then let it cool completely before removing the now straight filament stick. Easy and effective!
Hope this helps.