I've been shooting with the FX30 for about a year now and I also keep a smaller body for travel, so I totally get the struggle of wanting one rig for both. To be honest, if you're trying to keep the XLR handle on the FX30, you should probably skip the RS3 Mini. I tried it and balancing that top-heavy setup is a nightmare... it's just too tall for the clearance on the Mini and you'll find the motors straining if you don't get it pixel-perfect. If you're looking to save some cash but still want something that works effortlessly, I'd highly recommend looking for a deal on the DJI RS 3 3-Axis Gimbal Stabilizer. Since the RS4 came out, the prices on the standard RS3 have dropped significantly, especially if you look at the used market or open-box deals. It handles the weight of the Sigma 18-50mm f/2.8 DC DN Contemporary Lens like it's nothing, and the extra arm length makes balancing the FX30 with the handle way easier. Another solid budget-friendly option is the Zhiyun Weebill 3S Handheld Gimbal Stabilizer. It is usually a bit cheaper than the DJI equivalents and has a built-in fill light and a really comfy wrist rest which helps when you're lugging the heavier FX30 setup all day. It's much better for taller cameras than the M3S you mentioned. Basically, dont go too small or youll regret it when the motors start shaking under that top handle weight.

Just found this thread... honestly i would stay away from the mini gimbals for that fx30 setup. i tried it and the motors got super hot and eventually glitched out on me. i switched to the DJI RS 3 Gimbal Stabilizer 3kg Payload for the extra room. it handles everything effortlessly even with the handle on. it is a bit heavier but way more reliable for long shoots, ngl.