I recently upgraded from the standard 30mg plan to the 100mg.
Im finding the speed very inconsistent. I'm running BTW 10m to 30m normally and very rarely near 100. I'd say the performance is lower than the lower plan.
Also my dear is are all ping different speed. On the old service they where all similar. Now my Sony phone is fast, but my Samsung tablet is maxing out at 10m.
Any thoughts or help.
Speed tests should generally be run over wired link (to rule out wifi setup issues)
Different speeds to different equipment does suggest an internal issue.
When is the NBN due in your area (check on the NBN website)?
The Optus cable system is possibly experiencing a fair bit of stress these days as it heads towards being decomissioned in 3 years. Getting 100 Mbps may not be doable. If not then of course drop back to paying for speeds you can get.