High cpu usage while on windows but low ghz while gaming ?!

Hi   i have inspiron 3593 i5-1035G1 1.19 ghz and 8 GB of ram and Nvidia mx230 2GB ,, i prevoiusly had an issue which is all the games were lagging and getting serious fps drops , and it wasn't about a high demanding specs game , no it was happening even with an 2012 game like nfs most wanted ! , anyway i contacted dell support and you told me to turn off intelspeedstep in bios and everything went really fine and i could play fine ,,,, Now what im facing is i updated my windows which was 1909 to the newer one 2004 and im getting fps drops again in games like Valorant which btw i could play with 120 fps so no one would say it's not a gaming laptop or so -_- ,, the issue is not a gaming laptop or not , its about something wrong with ur product ! ,, 
* While im not using anything and just on desktop i found on task manager that cpu ghz between 2 and 3 ghz ,, while when i start Valorant it goes down to 0.99 ghz ! and of course i get annoying fps drop ,,, 

* On windows 10 1909 version it was the opposite , i was on desktop 0.99 ghz and while gaming 2 - 3ghz ,, 

So whats wrong ? what is different with this windows update and ur laptop ?? because many people have updated to 2004 version and they didn't get any issues ,, please i need some help , i've been searching for an answer for too long