I have 3 eVic minis and haven't had a problem with any of them. I used to screw my tanks in tightly, too. It really does cause a lot of problems. I've finally kicked myself of the habit. A good mod to use while working on it is the Cloupor Mini. It has to be the original black or silver before they added TC. They have a screw pin that you can adjust for your tanks. It really helped keep me from killing the center pin.
I love the iStick 60W and the iStick Pico. The 60W is taller but it's super cheap ($28), you can change the battery, and it's really sturdy. It's also comfortable to hold and use. I have 3 and haven't had any problems at all. If you want smaller go for the Pico. Same features but a lot smaller. I paid $19 for my last one. I bought it from here:
Eleaf iStick Pico 75W TC VW Box Mod APV - Brushed Silver
Authentic Joyetech eVic-VTC Mini 75W TC Box Mod APV - Black
I have 3 of the older eVic minis and they do work great. I love my Cyan set. The rest are all black with silicone sleeves. One is purple and the other is red.
All of my iSticks with built in batteries quit working. Even my 40 watts! The battery is fine in them. They all give me an error when I put an atomizer on them. The 60 watt has been the best for me. I've been using them longer and haven't had a single problem.
I just bought a bunch of atomizer coolers from Fasttech and put them on my mods. They'll save the threads and keep my tanks cooler. Some of them get pretty hot when chain vaping.
I've looked at the AIOs and they look nice. My favorite Joyetech mod is the original egrip. The GS Air coils fit it perfectly and it's a great stealth vape setup. The first one I bought has the OLED screen and uses Ego One coils. I bought an original replacement base for it so I could use the GS Air coils. I found an original egrip the other day on clearance from a US vendor for $21. It was just the mod. Not even a drip tip included. But I love it.
Sweet-vapes has great service. I buy coils from them a lot. I'm stocking up on 1.5 ohm GS Air coils since they can be rebuilt. I use a lot of the GS Air tanks. I have 1 Cubis tank on an eVic mini. It's a nice tank! I have my Lemon Ginger Iced Tea juice in mine.