For the investment, screen size, components, etc. and so forth.
The best Laptop for video editing is a Desktop.
If you have no other option but to edit and record using a 13, 15 or 17 inch laptop.
I wish you the best of luck. I don't recommend going there. They are just too darn small.
Some excellent comments in here (and a few off-topic; please try to stay within the confines of the OP's original question), so it's definitely appreciated. I think that "best laptop" or even just "best computer" for Camtasia will almost exclusively be limited to your editing behaviors, recording needs, and budget. We in Technical Support often see users with budget laptops being extremely successful with Camtasia, even more so after a little troubleshooting or coaching, while on the flip side I have seen an absolute beast of a computer just come screeching to a halt while trying to edit/produce a small project. I think that defining a budget is also an important step as it is very easy to just go a little overboard at times, so I'd like to put forth one of my personal (and in no way endorsed by TechSmith) recommendations for a very reliable laptop that is extremely proficient at handling what I throw at it while being largely affordable when looking at the scope/scale of power-to-price.
I personally use an MSI GS63VR Stealth Pro 4k and outside of some occasional heat concerns when playing a couple of different video games (and only once with Camtasia), it is literally a rock-solid machine that stands toe-to-toe with my desktop workstation at the office. I'd recommend taking a look at it if it falls within your budget.
Lenovo has come up a few times and I absolutely love their machines; rock solid performance, attractive case, generally affordable and feature rich. I used the same trusty Lenovo all through University and it worked pretty solid throughout. Dell I can't speak to as I've actually never used one of their laptops (but I have used plenty of Dell desktops) so I'll defer to the experiences of the other community members on that end.
Note though that some of the issues you are running into might be addressed with your existing hardware; it could be that there are editing behaviors or issues with source files that are causing the issue. It is entirely possible that the issue is hardware related as well; I would be curious to know if you have opened a Support Ticket at all? There are a ton of different things that could be a part of the problem so the Support team would be a good place to start.
Hope that helps!
note: the product opinions in this response are mine and mine along and not intended to be an endorsement by TechSmith