FPS usually is pretty much higher than anywhere else if you're in an interior (as you're describing) because it has to render much less.
I've had it too on W10 but got the (for me working) solution as I describe to you below:
It's a pretty long list of steps but as it's a high chance of solving this problem you may find it worth the effort.
First open MTA, go to settings and see if Disable driver overrides option is checked, if it is uncheck it.
- Use the latest driver on your onboard graphics. For your laptop get and install this: http://downloadmirror.intel.com/24973/a08/win64_153336.exe (also newer)
- Don't use the ''engineering sample'' of your dedicated GPU that comes with Windows 10, but instead use the most recent driver for your laptop: (http://support.amd.com/en-us/kb-articles/Pages/latest-catalyst-windows-beta.aspx > select win8.1 64 version)
- Update intel chipset: http://downloadmirror.intel.com/20775/eng/SetupChipset.exe
Now delete your gta_sa.set.
The problem may be related to DX12 and codecs, so get this codecs (http://www.codecguide.com/download_k-lite_codec_pack_full.htm) and select only codecs (excluding player) for letting it install systemlevel codecs only that you need.
Then open commandprompt (cmd) as Administrator, and enter & let run the following:
Dism /Online /Cleanup-Image /RestoreHealth
Make sure you're connected to the internet and you havent disabled Windows update and/or its service.
As soon that finishes reboot your PC, then again open cmd as administrator, then enter:
sfc/ scannow
Then again reboot your PC once its done. Now go to Control panel, then Programs and components and look left up for ''Turn on or off Windows features'' and look for Legacy components then disable/remove DirectPlay checkbox, let it disable, then reboot your PC and go to the same window and Enable it again and let it re-add DirectPlay.
Now use an DirectX updater, not the web installer but the full redist package: http://www.microsoft.com/en-us/download/details.aspx?id=8109 and let it install from after you extracted it on the desired location using DXsetup.exe.
Then open up your Intel driver configuration page, reset all settings to default (if you got nothing like important custom configs there) and select your default GPU to be used as ''powerful ATI GPU'' or something like that. Now blank your 3D/application settings, and if its visible set global settings to always use the ATI GPU, if you can enable this per application add Multi Theft Auto and gta_sa.exe processes in that list and do the same for it, apart from letting it use application's default settings. Also go to your ATI/Nvidia dedicated config page and reset everything to default, then do basicly the same thing: select it to 'Use application settings'' or similar on global and also on Application specific settings for MTA/GTA processes.
Did not work.
EDIT: Ignore what I said before. I just saw the link you gave for the Intel display driver. I downloaded and installed it and rebooted but when I check device manager it shows the version I first saw after installing Windows 10. I think the driver does not get installed properly.