Peninsula, Borneo or both
A classic first trip runs from Kuala Lumpur to the tea plantations of the Cameron Highlands, on to George Town in Penang and ends with a few beach days on Langkawi. Ten days to two weeks of that, with maps through George Town's lanes and photos sent at night, fits the 5 GB pack, which lasts 30 days. The 3 GB pack lasts 15 days and is enough for a long weekend in KL or a stopover on the way to somewhere else.
Adding Borneo means extra flights to Kota Kinabalu or Kuching and days away from reliable wifi, so 10 GB gives you room. The 20 GB pack is for a month or for working from a laptop through the hotspot. If you run low, top up the same eSIM. The data calculator works out a figure for your route.