Mention the specs of your PC and what version of VP you are using. What is the resolution of the bulk of the source files?
There's no longer a provision for PV resolution adjustment, but you can drag the window to smaller dimensions.
After the project fully caches (green line above the thumbnails) there should be minimal if any stuttering.
Under OPTIONS | EDITING tab, toggle the "Use Hardware Acceleration" item to see if that has an effect.
Verify that your video driver and Direct-X are up to date. https://www.nch.com.au/kb/10265.html
Let's take a look at your project and see how it performs here. It's easy, quick and can be totally private. Just carefully follow these four steps...
Share your project. Someone will take a look and come up with a fix. The process is easy, quick and can be done privately. Just follow these steps...
Back up --- With your project on the timeline, click on MENU at the top-left. Click FILE|BACK UP PROJECT FILES TO FOLDER. Choose a folder and SELECT FOLDER.
Upload --- Upload the saved, numbered FOLDER. Use a free server - Google Drive, MS OneDrive, etc.* Do NOT upload the individual VPJ or export file.
Get link --- Get a public link. If using Google Drive click GET SHAREABLE LINK. Change "restricted" to "anyone with the link can view" Click COPY LINK | DONE.
Share --- Paste that link here, or click the folder at the top-right of this forum to message it privately to me. It won't be shared.
* Before uploading, right-click the folder, click PROPERTIES. Look at the File Size to confirm that it's not too big for the free space on the server.