Well, like they say, the more the merrier. Syncing lower would be advised if your connection is unstable, airtel anyways caps the speed on your PPPoE user ID on their end. So, the sync rate doesn't do much, unless, the server fails to apply the cap, or the actual sync rate itself is lower than the speed provisioned, in that case you would be hard limited by your sync rate.
Yes, if you have 45Mb sync rate then you should be able to get 40Mbps. But, in the end it all depends on airtel, if their line feasibility doesn't show your line is good for 40Mbps, they simply won't do it.
Yes, if you have 45Mb sync rate then you should be able to get 40Mbps. But, in the end it all depends on airtel, if their line feasibility doesn't show your line is good for 40Mbps, they simply won't do it.