Generally, these screen freezes, also known as a form of stuttering, are caused by insufficient speed of data transfer along the pipeline between hard disk, processor / ram and graphics. It can be a slow hard disk (if your laptop has a mechanical HDD, this could easily be the reason - SSD upgrade would be a way to go), a graphics card which barely meets the requirements (especially VRAM, which is oftentimes a problem in laptops), outdated graphics card drivers, or other software that runs on your laptop in the background. For example, antivirus or web camera could take resources from the computer and overload it for a very short period of time on a periodic basis. When this short overload happens, Zwift would freeze for a moment. You could start by killing (or pausing) all nonessential programs that run in the background which are not system programs and which you do not need to run Zwift. This could potentially help. At the very least, you will find out if any of them was a culprit.
To answer your question, powerful laptops are usually sold under the name “gaming laptops”. This is probably because any hardware can run a web browser or Office these days, and very few people run demanding video or graphics processing software - so gamers end up being primary customers for high end hardware. If you need a high end laptop which can run graphics and animation really well, gaming laptop is the way to go. Or a high end office laptop priced in the $1500 range. Or you can get an AppleTV - it runs Zwift reasonably well from what I hear, it is quite inexpensive compared to laptop, and all that it requires is a TV.