For most fabrics, start with a 75/11 embroidery needle, drop to 60/8 or 65/9 for sheer material, and move up to 90/14 for denim, canvas.
Mechanical is the safer buy for straight seams, hems, and repairs, while computerized earns the edge once you need 15 or more stitches, one-step buttonholes, and saved settings. That answer changes fast if the machine travels to classes, sits in a small storage space, or handles thick seams every week.
Look for a bag that leaves 1 to 2 inches of slack around the project, opens at least 6 inches wide, and has enough structure to keep needles from poking through the fabric.
For quilting, look for 1,200 to 1,800 watts, a pointed soleplate, cotton and linen temperature marks, and a cord long enough to reach your pressing station without moving the board. Move up a tier only when repeated seam pressing, larger quilt tops, or frequent steam use slow a basic iron.