I've just installed Disciple 2 - ROTE via GOG Galaxy, game can launch and playable but it's not smooth. It's just like I'm playing with a very slow computer. I'm using laptop. My system is I7, 6GB ram, Windows 10 pro 64bit, Intel(R) HD Graphic 4000. Seems like compatibility issue?

Anyone has same issue? Any suggestion?

Use opengl wrapper (read instructions). Game is nearly unplayable without it on modern systems.
https://www.moddb.com/games/disciples-ii-dark-prophecy/downloads/disciples-wrapper-v160

GOG Galaxy version is broken. And they erase old builds even from private branchs.
Alyhough they looks like correctly update it (fixed) to DLC fontent and proper 3.01.

Offline version basedon peegious Galaxy build come with GOGDX Wrapper. Also have some usual for GOG compatibilities pre-set'ups.

You need configue this DXCFG.exe from GOG and game own ConfigEdit.exe (first is UseD3D and proper reslution which one in most cases 1024x768).
Still for a build without wrapper maybe there GOG still apply fullscreen optimisation. Another one to experiment is dpi scaling in same there exe file properties.

Ofc video driver should be srt to Keep Aspect ratio (everywhere should be on where there is such option). Galaxy and games should be NOT on system drive.
In any cases DXCFG and Config exe's should be started as "Run as admin".

DisciplesGL for further improvments. Main goal is widescren (widescreen hsck is optional addition and actually make worse). It is optional mod, not required. Im not sure it is or not better to have it for someone who just start play for the first time.
Still optional even as widescreen mod. Its just zoom-out map.

Third party wrappers require disable compatibilities that GOG pre-set to the games!

Upd: actually main feature of Verok's fixes-mods - make game worked in windowed only (borderless fullscreen windowed). So it is easier to Alt-tab.
Win8+ broke this game so you indeed need some wrapper. GOGs, Narzoul's or Verok's. WIth any of them should be no issues alt-tabbing. Without you can get black screen issue after return to game window.