Latitude 5480 with K17A docking station and two External Monitors

When you say K17A, are you referring to the Dell WD15 dock?  That's the result that comes up when I Google "Dell K17A dock", but K17A isn't an official Dell model name.  If the WD15 is correct, then as indicated in its product page, FAQ page, and manual, it can run dual displays up to 1920x1200 each.  That said, I suppose it's possible that there are restrictions around which outputs can be used simultaneously.  I've never tried the specific combination of HDMI+VGA because VGA is ancient and looks noticeably worse than any other output type because VGA is analog, whereas everything else these days is digital.  Considering that the P2719H displays you're trying to use also have DisplayPort and HDMI inputs, why not connect one of them via HDMI and another via a Mini-DisplayPort to DisplayPort cable?  I personally have successfully tested dual 1080p displays through a WD15 using that combination of outputs, and you'll get a sharper image than using VGA.  That said, a 27" display with only 1920x1080 resolution isn't going to look great for another reason, namely low pixel density.  Even a 24" 1080p display has slightly lower pixel density than the "normal" 96-100 dpi range, so stretching those pixels out across a 27" display area makes that worse.  That's why the vast majority of 27" displays use 2560x1440 resolution, although the Dell WD15 can only run one display at that resolution.  The only time I've used 27" 1080p displays have been for kiosk setups running PowerPoint decks or videos where size matters and sharpness doesn't because the displays are meant to be viewed from a distance, and then with people who have relatively poor eyesight and therefore want things to be bigger rather than sharper.