Well, for starters, change these lines...
output=overlay
You could also try ddraw and Opengl. For ATi cards overlay and ddraw seem to be the best. For nVIDIA cards, you can try Opengl. In my opinion, I like overlay most, because I do not like bilinear filtering used in ddraw and Opengl (although there is also a Openglnb - without bilinear filtering).
Then adjust speed:
core=dynamic
cycles=auto
There is also an autoexec section at the end of the file. It's used to auto execute parameters when starting DOSBox. Mainly used for writing mounting commands there.
E.g.
mount c c:\oldgames {The Hard disk}
mount d h:\ -t cdrom -iotcl {The CD-ROM}
Exit and save changes.
Intel i7 5960X
Gigabye GA-X99-Gaming 5
8 GB DDR4 (2100)
8 GB GeForce GTX 1070 G1 Gaming (Gigabyte)