Common settings to speed up render time?

Hello everyone!
I just tried out DaVinci Resolve 15.
My guess is that I made some beginner mistakes.

The problem is, that rendering videos take 3 times the amount of time they did in my old Power Director 16 Software.
I use CUDA with my NVidia GTX 650Ti, operating on an SSD and on intel-i5-7500.

Usually, I have a couple of Screen Videos of games, taken by Win10's DVR as H264 in mp4. All files are already cut.
What I do is put them all on a timeline, add the same transition between all and lay an image on top to hide some screen parts.
All sources are 1920*1080 resolution at 30fps.
This is also the target format.

In Power director I was able to render 17 Minutes of a film within 9 Minutes. In Davinci Resolve it took 24 Minutes.

Is there some setting that I missed? Maybe somehow switching off the preview window?

H.264 files are tough to play because of the overhead they require from the system. Resolve needs a lot of power to do what it does, and when it gets bogged down with difficult formats like H.264, it can be like molasses.

Picking the right format for post is one of the cornerstones of good workflow, and what I try to do is convert any H.264 to something like ProRes or DNxHD prior to the start. Those generally work very well and allow the system to work in real time.

Thanks for the answer!
I could always convert the source files to DNxHD prior to processing...

If rendering DNxHD files can be easily done in real time, a 17min video will then take 17min instead of 24 min to render. So, if converting all the source files (12 files in this case) takes longer than 24-17=7 minutes, there is no gain timewise.

But isn't there a way to render faster than real time?
Power Director seems to render with something like double the framerate.

i've heard there's a speed boost in h.264 encode/decode in the studio version, my systems are licenced, and i run out h.264 screeners @ HD around 200Fps if it cached, or the source files can keep up