That’s Z-Offset. When I start a print, I do a skirt or brim with three to five lines. And while it is laying down the skirt, I use the touchscreen to fine-tune the Z-Offset. The individual skirt/brim lines should connect and be squished down, but not so much that material evades to the sides. Here are some pages from the net which illustrate this well:
The last page has a very good photo:
Nah, not really. Speedwise for PLA I use 50-60 mm/s for first layer, 100-120 mm/s for the rest (I’m an impatient man who can live with some imperfections - doing mainly functional stuff - you may want to stay below 100 mm/s if you want it look nice…), and that usually works. Temperature is something to test out - either with a temperature tower, or by running a print and see if I’m happy. Values on the spool are for orientation IMHO 
Say what you want about Luban, but reading what others post the default profiles that Luban provides seem to work for many people - did you try if you succeed with them?