I installed it in qemu and using soundhw all flag with qemu. I don't know what other information to provide as I'm new to OpenBSD. Also videos don't play sometimes in Chromium or Firefox. Both were installed through pkg_add. Audio is very noisy.

"-soundhw all" enables many different virtual sound cards simultaneously, so this might not be an optimal provisioning. I recommend selecting only one virtual sound card at a time to determine which is the optional emulation. You might start with "-soundhw hda" which emulates high definition audio. From there, you can then test the guest VM's audio provisioning with something very simple, such as playing an audio file with aucat(1) as described in the multimedia chapter of OpenBSD's FAQ: http://www.openbsd.org/faq/faq13.html.

(Qemu emulation is unlikely to be the best way to investigate OpenBSD's multimedia capabilities, whether audio or video.)

I had similar problems with OpenBSD 6.6. Solved with installation of pulseaudio. This required few extra steps but eventually worked well.
OpenBSD and multimedia is not a best match. Multicore cpu support is rather rudimentary.
These are observations from VM (full screen) but I doubt that bare metal installation will really improve. Playing wideo in vlc works ok, but youtube in firefox just stutters.