May I ask which Sony soundbar you got?

If you could do it over again, which one would you have gone for?

Thinking of a Yamaha soundbar.

That's because, if you did a bit of research: the CT260 is notorious for subwoofer lag.

The sub does not blend well with the soundbar simply because of the lag, you can minimize it by putting them side by side but even then, it doesn't help due to its poor implementation on its wireless frequency.
Many other soundbars employ their own frequency to work with the sub (not the standard 2.4ghz/5ghz wave), Sony doesn't... for whatever freaking reason.

Most HTIBs these days has at least an optical input on its Blu-ray player. Many even has HDMI inputs.
It is as straight forward as it can be, don't know why it's confusing. TV > Blu Ray player > speakers. That's it.

That depends on how your living room/bedroom is setup to be like. The shape of the room and the size most importantly.  Other factors are important too, but that's another topic.
A lot of people jump into a 5.1 setup without first looking at their room then ended up with dissapointing results. Sound bounces off objects and reflects off walls.

I've always believed that soundbars are meant for small bedrooms or small SOHOs.

LG NB4530 if you don't want to go above RM1.2k.
Other than that, you could want for the upcoming CT330 which shold be around the RM1.3k mark or lower.

Above that, I'd suggest starting to look for custom 2.1 setups.