Is it just editing standard flat video without heavy effects? Some effects need a better GPU.
Make sure you have the Cache on SSD and try shutting down other programs that use the CPU intensively. Also things like 24GB RAM and i7 may sound nice but don't really say anything at all. You need RAM with a decent speed preferably around 2000Mhz (thougyh 1600 works fine for me to be honest) and the number of cores on your CPU helps as well. The new computer you bought seems like an odd choice for video editing... I edit my 4K footage on a PC without any dedicated graphics card at all without any issues. Going from i7 to i5 sounds like a step back, as well as 8Gb RAM which is about half of what you would ideally want to start with.
Have you put your setting within Premiere right?
The cats are watching us...