All of these problems are caused by TwitchApp not grabbing all the available unused system ram to give to Java.
You can fix it by doing the following:
You have to open the profile by right clicking the icon and choose view profile. Then on the next screen in the upper right, click the 3 dots button "..." and choose "profile options". On the popup, unlock system settings and slide the slider to allocate more RAM, if you can spare it. Hit ok, and start the pack.
If you still are having issues, especially if your allocated RAM is filling up in Minecraft (hit F3 and check the memory lines in the top-right corner), then add the following java arguments in the same location specified above in your TwitchApp:
-d64 -XX:+UseG1GC -Dsun.rmi.dgc.server214748.gcInterval=2147483646 -XX:+UnlockExperimentalVMOptions -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=32M
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