Can vouch for this

Tbh I definitely agree with the diy approach mentioned earlier. It’s a bit of a rabbit hole but honestly so rewarding if you have the patience for it. When I first started with my current setup, I was super intimidated by the balancing act - literally. A few things I learned the hard way:
- Balancing is like 90% of the battle; if it's not perfect, those motors will scream at you.
- I actually ended up making a custom counterweight because my setup was too front-heavy with my main lens.
- Calibrating the dead zones and motor stiffness myself instead of using the "auto" settings saved my footage. Not 100% sure if that’s the route you want to go, but basically, getting hands-on with the setup made me understand the physics of my a7 IV way better. Just be prepared for some trial and error - it's a learning curve for sure!

tl;dr: Grab the DJI RS 3 Mini. It fits your budget perfectly and handles the a7 IV weight easily as long as you arent using massive telephotos. In my experience, the RS 3 Mini is the most reliable tool in that price bracket because the software is actually intuitive. Most people struggle with micro-jitters on smaller gimbals, but the stabilization algorithms DJI is using now are just miles ahead. The real trick to getting that 'pro' look though isnt just the gimbal... it's the weight distribution. I actually spent the last few weeks messing around with a DIY shoulder rig I built out of PVC pipes and some old weights from a thrift store. I know it sounds ghetto but adding that physical mass makes the movement so much more natural than any motor ever could. I even tried mounting the gimbal to the PVC rig for a weird hybrid setup. It looked ridiculous, kinda like a sci-fi prop gone wrong, and my neighbors definitely think I'm crazy for walking around the yard with it. But yeah, if you want something that just works without the workshop time, go with the DJI.

DJI Ronin SC2. Unfortunately, had issues with Ziyun. The Ronin's been solid for 2 years now.

A7IV's tricky. Payload is key. Zhiyun Crane M3S is decent option; its updated motor handles the camera with a smaller lens setup. Check its 1.76 lb capacity carefully, though!

DIY stabilizer? Might need practice. Zhiyun Crane M3, $400, could be a starting point.