The way I'd tune my printer would be to first get the extrusion multiplier set to its optimum value:
Find a calibration cube ( or generate one) and set the Top Solid Layers to nil and Outline/Perimeter Shells to 1(both on Layers tab) and Infill Percentage to nil. Set your Extrusion Width to what you want it to be (Auto...which will be 1.2 time nozzle width, or whatever manual setting you want...but don't go less than nozzle size or greater than 50% greater than nozzle size) and initially set the Extrusion Multiplier to 1.00.
Print sufficient of the cube so you have enough to measure the wall thickness. Remove the print and see what the thickness is. If its less than your setting, increase the multiplier, if more, reduce the multiplier. Print again to see what the effect is. Repeat until you get the right extrusion width.
Now you have the extrusion width set, you can take a look at the bottom surface. Look at the last test you did. Is the bottom smooth? If it is, then check for a small ridge indication plastic being squashed sidewards around the edge of the first layer. If there is one, your nozzle is a tad too close to the bed. If the bottom shows lines like in the photo you attached in your first post, then your nozzle is too far away from the bed.
If you bed is level, an accurate way of adjusting the height is to alter the Z-Axis Global G-Code offset. Adding to it or making it positive lifts the nozzle up; subtracting from it or making it negative lowers the nozzle. Adjust the value to adjust the nozzle height in the direction you've identified by half your layer thickness....and try printing. Adjust and print (by smaller values if necessary) to get the optimum finish.
You should now have a good starting point for developing your print settings to get cleaner and more reliable results.
And try this video for supports:
https://www.simplify3d.com/support/tuto ... tructures/