I recently Sharpened a few knives to 15 degrees. They're not holding an edge like I'd like them took. I'd like to know if it's going to cause any issues if I reshape them to 20*
You might try a micro-bevel e.g. just widen the angle to 20° per side and do a few very light strokes with the stone of your choice. You can choose just how toothy you want the micro-bevel to be. You only need very light pressure and just a few strokes to create it. With this technique, you can still benefit from having thinned the shoulders of the edge to reduce drag while cutting but gain increased strength at the edge from the wider angle.
If basically be creating a double bevel wouldn’t I?
Your cutting bevel would be 20dps but would have the advantages of the thinned out shoulders as clay said for slicing easier. I have been putting micro bevels on all my EDC knives and have convinced customers to do it also. Not so much a double bevel but with having the micro bevel your able to keep a good edge on it with having the thinned out shoulders. Keeping the shoulders thinned out helps down the road on repeated (Micro Bevel) sharpening’s so your not getting up into the thicker points of the blade.