You should check the the tutorial about screen sizes : construct.net/en/tutorials/supporting-multiple-screen-sizes-17
It will possibly give you enlightenment regarding what ratio to use in your project.
I've already linked the performance and other manual tips you should check out and implement in your game.
Also, as I have tested and did not encounter the same issue you do, and apparently no other user viewing this topic did either, it is likely an issue with your own computer/hardware, and not with our software.
No "help page" can help you further than the answer already provided in this topic for you to follow.
As mentioned, the "line sprite" issue is an old issue regarding wrong/poor graphic card drivers. Are you sure your graphic card drivers are up to date ? Are you sure your card delivers WebGL/WebGL 2 ?
The age of the card is not what matters, the features are.
Are you sure your browser is making use of your graphic card and not using an integrated chipset instead ?
You would have to "force" windows to use your graphic card instead of the chipset.