High Ping issues on TD-W9970

Whilst talking on the fibre forums about my upcoming fibre connection people told me that i should replace my DSL-ac68u due to the bad DSL chipset it has in it so after some recommendations i decided to switch to the TD-W9970 as my modem and then bridge it and use my ASUS as a router only.

I am using it on ADSL currently as my due date for VDSL is 29/07/19 and i have seen an increase in max rate from 4704 to 7366 with the TD-W9970 which i am over the moon with. However when im playing games sometimes my ping will shoot up to 1000+ for about 30 secs and then come back down to normal. Obviously this isnt ideal and i've never had ping issues on the AC68U only the odd connection drop every now and then.

I did test it out by switching back to using the ASUS and the ping issues seemed to vanish. I'm not sure why it is doing this. Is it the link between the routers? Is it just because my line is not that great? Will these issues disappear once i move over to VDSL?

Just looking for some help on what to do or whether i should just wait until VDSL gets here.

Max rate changed, but has actual sync rate changed? It may be that there are batches of retransmissions due to errors from pushing the ADSL2+ closer to the limit.

Yes sync rate has increased from 4480 kbps to 6731 kbps. The upload has stayed the same as it was between the two modems at 448 kbps.

I'm guessing then this will all be resolved when VDSL turns active then if its possibly related to ADSL. Just wanted to make sure that the new modem wasn't faulty.