The top speed in SC is 2001c (All together now.... Ta-dadada Daaa... Ta-da! Ta-da! Ta-dadada Daaa... Ta-da! Ta-da! ...)
A few tips:
2 methods of exploring that I favour are...
Pick a far away interesting destination (nebula, cluster, known black hole, etc) and go there in "fastest route" mode, then then switch to economical mode and wander around looking for interesting stuff and scanning it, then head back.
Pick a direction (plot a route to anywhere beyond occupied space) and go there in fast mode, until you hit unexplored systems, then switch to economical mode and wander.
In both cases, when you start wandering, pick destinations with stars more likely to contain interesting stuff (Type G, F, K and sometimes A or B for metallic planets and water worlds; Type O, B and maybe A for neutron stars & black holes)
Class M stars generally tend to be boring, but some of them may surprise.
When you enter a system, throttle to zero and target the main star as soon as it shows on your radar. While it's being scanned, ping the system with your discovery scanner then look at the system map. There's a lot of info there, even before you scan the planets close-up. Look at the planet graphics:
Asteroid fields are worth nothing. Ignore them.
White(ish) planets (often pink around brown dwarfs) are iceballs. Don't bother.
Blue tend to be water worlds - very high value (but sometimes they're ammonia). Icecaps may also indicate the presence of water
Dark grey is metal-rich - high value. Most other colours are either high metal content (medium value) or rocky (low value) but sometimes even these can be terraformable (check the distance (AU) from the star, and the type of star - "Goldilocks zone"), which increases their value.
Dark with red bits is young/volcanic. Could be metal rich high metal content or rocky, but (I think) worth less since the metals are hard to get at, being so hot.
Planets with clouds have an atmosphere - Hit or miss, but could be worth a look.
Gas giants are generally boring, but it may have life which makes it interesting for scientists, so a slightly higher value. (If it has spots, this MAY indicate a higher probability of life, but I'm not sure.)
Apart from the type of star, the name can also give you a clue. e.g. "HIP 1234" might be more interesting than "Szeriouszlyunpronounszable Sector qwerty-348495 X-573"
Always know where your towel is.