Combining gauges (piecing two patterns together)

#1

The sweater I’m working on calls for 18 sts and 24 rows = 4 ins [10 cm]. The pattern I’m planning to intarsia onto the from calls for 4.1 stitches/inch and
5.26 rows/inch on size 9 needles. Can I work the intarisa pattern on the sweater gauge?

#2

I’m assuming the intarsia pattern is on a grid. I would just knit the stitches of the intarsia pattern with the yarn size I’m using for the sweater. It may not come out the same size as the original, but I don’t know how you’d knit a motif at a different gauge than the rest of the sweater. It’s not really that much different anyway, is it?