6L6

Bridged can swing more voltage, parallel can push more current. Depending on your speakers, one of these ways will work better than the other, or one way will sound better to you. So try both.

Speaking in broad generalities, bridged will, in theory, work better with higher impedance speakers, and parallel will work better with lower impedance speakers.

BUT, try both and see what you prefer.

Add either a balanced line driver or a transformer.

The photo is correct. The orientation matches the silkscreen. The flats of the transistors face each other.

Again, this isn’t the place to troubleshoot. Post in this thread please.

https://www.diyaudio.com/community/threa...

Wattage is fine. You’ve got a wiring / stuffing / soldering error somewhere. Post a series of well lit, in-focus photos in this thread with a description of your problem.

https://www.diyaudio.com/community/threa...

Please post some photos of your build, particularly the inside back panel, in this thread - https://www.diyaudio.com/forums/pass-lab...

Please take some photos and post them to this thread - https://www.diyaudio.com/forums/the-diya...

Remember the PCB mounts to the top panel and all the components hang from the inside.

The amplifier circuit is inverting, so wiring it as intended and shown (with speaker red on ground) restores absolute phase.

Attach your speakers normally - red to red, black to black.

https://cdn.shopify.com/s/files/1/1006/5...

Both ways will work fine. If one was forced to choose, wire as shown the photo.