Deluge
So I figured out the cause. It is totally the display scaling set on your monitor.
In windows if you go into your Display settings, and find scale. If you are not set to 100% then the webui autoadd config window will be useless. If you then change this to 100% then refresh the webui and try again "tada" it works. I can replicate the issue by changing the scaling or moving the web window to a monitor that is not display scaling. PS my resolution was at 1920x1080, laptop screens tend to display scale.
Super weird bug
Autoadd broken in WebUI
Re: Autoadd broken in WebUI
While this is odd, I'm not entirely sure you could attribute this to as much a bug in Deluge or the plugin as a quirk of Windows Display scaling (in this particular case - not sure if it would affect Linux or whatever) or browser.
I'm not sure what API's or settings are accessible for the browser or system-wide in regards to this, but I think it is possible to address this perhaps with using some sort of CSS as a percentage rather than definitive amounts, but I'm not sure - I'd need to test this.
I'm not sure what API's or settings are accessible for the browser or system-wide in regards to this, but I think it is possible to address this perhaps with using some sort of CSS as a percentage rather than definitive amounts, but I'm not sure - I'd need to test this.
Re: Autoadd broken in WebUI
@knelllemon, Awesome, now I can finally reproduce, thanks buddy! 
I'll look into it one of these days and hopefully fix/workaround it, create bug-ticket and upload build in meantime, hopefully. I btw tested my previous posted build, and it still opened small and badly despite I had forced it bigger in code - the code I added for now allowing manual height resizing did work, but sadly the actual widget inside window still small and borked, inside the now bigger window, so need more looking into, but atleast I can see what's going on now, which indeed is kinda nice for troubleshooting lol 
Thanks again.
@ambipro, You called it from beginning as a host display resolution related issue, nice Anyway, the buggy widget drawn are from pretty old extjs version deluge includes, so might be related to bug therein, or quirky windows/browser as you stated.
I'll look into it one of these days and hopefully fix/workaround it, create bug-ticket and upload build in meantime, hopefully. I btw tested my previous posted build, and it still opened small and badly despite I had forced it bigger in code - the code I added for now allowing manual height resizing did work, but sadly the actual widget inside window still small and borked, inside the now bigger window, so need more looking into, but atleast I can see what's going on now, which indeed is kinda nice for troubleshooting lol Thanks again.@ambipro, You called it from beginning as a host display resolution related issue, nice
Anyway, the buggy widget drawn are from pretty old extjs version deluge includes, so might be related to bug therein, or quirky windows/browser as you stated.Re: Autoadd broken in WebUI
OK I fixed the issue and will make a ticket later, and meanwhile here's a fixed build, taking precedense over default: AutoAdd-1.9.egg (just add as any other plugin, and don't need overwrite original in deluge source - you can see it took precedense by checking it's now upped version number in webui plugin prefs - need restart deluge(d) obviously, if dropped into plugins subfolder of deluge config)
However, I also found that you can just temporarilly zoom your browser down to 80% and refresh page, and then zoom back again when finished messing with plugin config, which is little easier than disable and reenable scaling in windows display settings, i.e. just a few ctrl+-/ctrl++ key strokes.
Anyway, thanks again knelllemon for your nice tip there, making this at all possible for me to look into, and as said, i'll create and edit in a link to a ticket soon'ish.
Edit: Done, PR(instead ticket, since simple so not high chance of embarissing myself ) here: https://github.com/deluge-torrent/deluge/pull/444
However, I also found that you can just temporarilly zoom your browser down to 80% and refresh page, and then zoom back again when finished messing with plugin config, which is little easier than disable and reenable scaling in windows display settings, i.e. just a few ctrl+-/ctrl++ key strokes.
Anyway, thanks again knelllemon for your nice tip there, making this at all possible for me to look into, and as said, i'll create and edit in a link to a ticket soon'ish.
Edit: Done, PR(instead ticket, since simple so not high chance of embarissing myself
) here: https://github.com/deluge-torrent/deluge/pull/444