Mouse

cursor position update is performed in the background at low priority, so as not to waste CPU power needlessly updating the cursor position far faster than human threshold of perception.

When your Mac is over-taxed, by using all its available CPU power, or by using up all the memory and spilling stuff onto Swap area on the boot drive, cursor position updated can lag.

By far the easiest way to cause poor performance, instability, and crashing is to install ANY third-party speeder-uppers, Cleaners, Optimizers, or Virus scanners. or a VPN that you installed yourself.

You should remove any and all (other than Apple built-in) virus scanners, speeder uppers, optimizers, cleaners, App deleters or VPN packages you installed yourself, or anything of that ilk.

Third-party file Sync-ers such as DropBox, BackBlaze, OneDrive, or GoogleDrive can ruin performance, but are not inherently dangerous.

Rather than play 20 questions, I suggest you download this little "discovery" utility, EtreCheck. it fixes NOTHING. Its entire reason for being is to create a report, already laundered of any personally-identifiable information, that is clean enough to be posted back to the forums for Readers to analyze and make recommendations.

Using EtreCheck to Troubleshoot Potential… - Apple Community

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"dragging badly"

That could mean a lot of different things to different readers.

Please elaborate. What EXACTLY is the symptom you are seeing.