I don't have the same machine as you but have you tried using a wss topper?

If you read your instruction manual, there should be a chart covering this topic including the types of thread to use. The videos don't cover everything that makes reading homework and practice required. I've been sewing over 45 years, hand embroidery even longer, and still go through the manual page by painful page with each new machine. Technology makes every machine different with the little details adding up to big problems and frustration if you don't read the manual several times, study, and practice the manual.

A good test for your machine is to do a zigzag satin stitch test stitch using your fabric sandwich sample. When you get a good, even satin or zigzag stitch, you will get a good stitch on the embroidery side. I discovered this during one frustrating embroidery session, started looking for a solution and playing around on the sewing side, and discovered it works.

THANK YOU!!!! I have now tried using the topper (sorta reminds me of saran wrap) and it really helped a LOT! I looked in my manual, and can't find any "helps" about the thread tension! I thought someone might just have a magical answer for me!
THANK YOU AGAIN!

To save you time and material, it does pay to do test samples before you do the final design. The stabilizer manufacturers and many websites have charts and instructions on what to use.

If you download a free design and unzip it, there is usually a read-me file giving design information and color changes.

Bobbin thread showing through rarely happens with my Bernina Artista, but when it does, I use a Mettler 60 weight bobbin thread that matches the upper thread. I recently did a Loralie design where everything was fine except the dark red, so I put red bobbin thread in. Magic! You can also use fabric pens to fill in the white areas. And if you do any free-standing lace, use the same thread in the bobbin as you use for the upper thread (I use Isacord Poly exclusively b/c it doesn't fade, bleed, washes well and is strong).

If your seeing the bobbin, your top tension is too tight or the bobbin is too loose, most likely the top is too tight. Just back it off 1 or 2. If your saying you see the FABRIC through the design, then increase the density in your pattern. If your using PE software, it is famous for fills being too light, 114 lines/inch just won't cut it for most fabric.

with the 270 the thread tension is controled with the nob on the head of the machine see page 52 and 141 in your book. stabilizer wil be a bigger help. i find it a Good Idea to try out stitches on similar fabric until i know how to set it and what stabilizer works. you have to practice and you ahve to look it up. brothers website has tutorials and projects ...