It's often said that the number of fonts you have loaded on your system the slower Corel will be. I haven't had much of a need to reduce my number of fonts as I either haven't experienced any lag or I just have gotten used to the speed at which the software runs. We usually download fonts onto our network so each designer has access to them as needed. I've always just navigate to the font, right click choose install. Any other method doesn't make sense to me. "Don't actually load the fonts" . So when I'm designing I can't experiment with what fonts look best? How would you use a font without it being installed first?
I don't like installing fonts directly into the Windows OS fonts folder unless they're fonts I am going to be using on a frequent basis. Too often I run into hassles uninstalling fonts. Windows sometimes blocks the attempt, saying the fonts are being used by the system. Font Managers can get around that problem.
Of course it's complicated on how to get the best performance out of Corel Font Manager. The quantity and quality of font files included in a target folder will dramatically affect performance. Generally professional quality commercial fonts are going to load and preview much better than those from free fonts web sites. Font Manager will tend to choke pretty hard on clip art fonts -the ones with complex vector images in each glyph window. ITC Dingbats or the old Common Bullets font aren't bad. Most symbol fonts work okay, just as long as the glyphs don't get too complicated.
System hardware is also important. I just did an upgrade on a 9-year old personal notebook PC. I had been planning to buy a new, higher end notebook. But I'm still in wait and see mode (waffling between the new Dell XPS 17 and Razer Blade Pro 17). Plus I have some medical bills to pay after a stupid lawn care accident 6 week ago. Keeping the old notebook running seemed like a prudent idea. The original 750GB HDD was starting to fail, causing boot issues. I bought a USB to eSATA cable to retrieve any important data I didn't already back-up. I ordered a Crucial MX500 1 terabyte SSD. And I learned this old notebook could support 16GB of RAM. So I got a pair of 8GB modules (also from Crucial). Very easy upgrade to install. Installed Win 10 Pro using the Win 7 Ultimate key that came with the computer.
Getting to the point, Corel Font Manager runs a lot better reading a font collection folder from an SSD than an old fashioned platter-type hard drive. The whole computer runs a LOT better with the SSD and RAM upgrade. The launch time for CorelDRAW 2020 is almost tolerable.
When you use CFM to install fonts it installs the fonts into Windows. You can use fonts in CorelDRAW that are registered in CFM without installing them but I choose not to do that. I have issues with that thought process. If I open a file from my network on a laptop to take to a client and CFM does not install those fonts to Windows when I get to the client I don't have my fonts.
I never use font embedding because it has at times caused serious issues when the embedded font also resides in Windows.
If you're having issues uninstalling fonts from Windows it's because applications are not releasing memory correctly.