The A3 was more of a tactical bomber but the weapons carrying capacity would most likely be equivalent...
As of now, we still can't even be sure of whether there is singular large weapons bay on the J-XDS (like those on the J-20 and J-35/A), or a dual split smaller weapons bay on the J-XDS (like those on the F-35A/B/C).
That is to say, without knowing the dimensions and rated load capacity of the weapons bay(s) on the J-XDS, it's rather pointless to make such a claim.
point is it was a carrier based bomber of some sort
Nope. In contrast to the A-3, which is very much a carrier-based bomber from the get-go - The J-XDS is designed and engineered to become a land-based and carrier-based fighter in the first place. Only if the weapons bay(s) is/are large enough, then the anti-ship or land-attack capability would come as an added bonus.
The differences in terms of how both warplanes were designed, engineered and used are pretty massive, so it's pretty much useless trying to equate them together.