Arrange elements in PlotLegend

Question

I have the following test code

Plot[Evaluate@Table[Sin[i*Pi*x], {i, 0, 10}], {x, 1, 20}, 
 PlotLegends -> 
  SwatchLegend[{"#0", "#1", "#2", "#3", "#4", "#5", "#6", "#7", "#8", 
    "#9", "#10"} , 
   LegendMarkers -> Graphics[{EdgeForm[Black], Rectangle[]}], 
   LegendLabel -> "Legend", 
   LegendFunction -> (Framed[#, RoundingRadius -> 2] &), 
   LegendMargins -> 2], Frame -> True, 
 LabelStyle -> Directive[Black, FontSize -> 20], 
 FrameLabel -> {Style["\!\(\*
StyleBox[\"x\",\nFontColor->GrayLevel[0]]\)"], Style["SIN"]}, 
 ImageSize -> 800]

I would like to achieve two things:

1. Arranging the elements in PlotLgends such that in the first column there are six elements and on the second the other five;
2. Changing the FontSize different from that of the plot, I would like for example to make it smaller.

Answer 1

Plot[Evaluate@Table[Sin[i*Pi*x], {i, 0, 10}], {x, 1, 20}, 
 PlotPoints -> 100,
 MaxRecursion -> 5,
 PlotLegends -> 
  SwatchLegend[
   Style[#, 10] & /@
    {"#0", "#1", "#2", "#3", "#4", "#5", "#6", 
     "#7", "#8", "#9", "#10"},
   LegendLayout -> {"Column", 2},
   LegendMarkers -> Graphics[{EdgeForm[Black], Rectangle[]}],
   LegendLabel -> Style["Legend", 12], 
   LegendFunction -> (Framed[#, RoundingRadius -> 2] &), 
   LegendMargins -> 2,
   LegendMarkerSize -> 10],
 Frame -> True,
 LabelStyle -> Directive[Black, FontSize -> 20],
 FrameLabel -> {Style[
    "\!\(\*
StyleBox[\"x\",\nFontColor->GrayLevel[0]]\)"], 
   Style["SIN"]},
 ImageSize -> 800]