The X98 Air 3G has 3G (obviously) and HDMI…
The general view seems to be that the Teclast ones tick all the boxes for features, but don’t always implement those very well. The stock Android ROM is a bit bloated, the screen on the X10 HD is poor in sunlight, etc. Whereas the other manufacturers sometimes do one thing very, very well (eg. having an excellent Android stock ROM) but then go and mess up one thing badly (dual-OS tablets with 32GB flash are really a mistake).
The other one I’ve been looking at is a second-hand Dell Venue 11 Pro 7130. That’s a far more powerful system (Core i5, 8GB RAM, a real SSD instead of an eMMC). Unlike pretty much any other tablet, Dell has left a few user-replaceable parts, so you can get one without 3G (3G versions are rare) and drop a 3G card into it. The downside is that it’s a Windows tablet, and efforts to make it run Android have not been very successful so far.