This is an anomalous question. Latency is the inverse of throughput so it generally follows that a higher throughput network will have lower latency.
I doub't , since you suggest that at 10 Mbps, on the same network, you get a lower latency compared`````````````` to one at 1 Mbps
Why do you doubt it? I suggest exactly that. Assume I have 10 Mb to send over two ideally identical networks of capacity 10Mbps and 1 Mbps. The time for transmission over the 10 Mbps link is 1 sec while it's 10 sec over a 1 Mbps link. If I'm interested in the last byte of the transmission I'll wait 10x longer if the data is communicated over the 1 Mbps link -- i.e. data transmission latency is higher.
I suspect you're confusing minimum communication latency with transmission latency. The minimum communication latency is the minimum time required to transfer a byte across a link. In this regard, given two otherwise ideally identical networks, the determining factor is the length of the link. So, for the example above, if both networks were for example, point-to-point fibre and the 1 Mbps link was 1 m long while the 10 Mbps link was 300*10^3 KM long, a single byte transmitted over both links at the same time would take 0.00 sec to get across the 1 Mbps link and 1.00 sec to get across the 10 Mbps link (determined by the speed of propagation of light).
However, note that transmission latency of the 1 Mbps link is lower than the 10 Mbps link, so if you were to start transmission of 10 Mb over both these networks at the same time you would receive the last byte of the transmission in 1 second over the 10 Mbps link and 10 seconds over the 1 Mbps link. The link with the higher minimum communication latency still wins.