I'm not sure of the sound on your Soundbar but if its a half decent one it will sound better than your tv built in ones , it may say Dolby atmos on the A90j but that term would be very loosely used as know tv speakers are that good when compared to a dedicated set up or good soundbar so don't expect the tv atmos speakers to be bouncing off the ceilings or you'll be disappointed.
As above the TV has Sony’s XR ‘spatial’ audio processing over and above a conventional TV - the spatial audio processing can be applied to all input formats.
The TV includes eARC which means you can pass Atmos audio from a connected Source or streaming App to an eARC Soundbar or AVR via HDMI.
Where your Soundbar lacks eARC you are limited to non Immersive audio formats.
Will the Sony XR audio processing sound better than using your Soundbar? You’ll need to swap between the TV speakers and Soundbar to know which works best in your room, longer term you may want to consider upgrading to a Soundbar which supports Atmos (if your room/room layout is appropriate).
I tried to use an ATMOS 2.2 TV with a 2.1 soundbar & it was such a conundrum, because the 2.2 in the TV sounded great for Presence, but there was NO bass response.
The soundbar had the bass response, but not presence.
Getting the two to work together was only accomplished via bluetooth & then there was always a faint out of sync issue, no matter how much I tried to adjust for it.
Eventually I went ahead & got a soundbar that's capable of ATMOS & DTS:X, much happier now.