Could be that TOS is more of a resource hog.
I have not found that to be the case. TWS seems a lot more resource heavy during boot-up than TOS.
Your hardware specs are more than enough. There is not that much difference between a i7-9700 vs i7-4700 for single-thread performance:
https://www.cpubenchmark.net/compare/Intel-Core-i7-9700K-vs-Intel-Core-i7-4770K/3335vs1919
You have plenty of RAM and I drive 2 full HD monitors easily with integrated graphics on my i5 laptop with both TWS and TOS.
Go to your thinkorswim directory and look at thinkorswim.vmoptions
-Xmx768m
-Xms32m
-Djava.util.Arrays.useLegacyMergeSort=true
-Dawt.useSystemAAFontSettings=lcd_hrgb
-Dsun.net.http.allowRestrictedHeaders=true
-classpath/p launcher-second.jar
-Djxbrowser.logging.level=INFO
-XX:MaxPermSize=256m
Above are the settings that I use. Can use much more than 768m if you want, but I have not found it to make a difference.