If you have two days to spend in Bala, you should definitely explore the beautiful Lake Bala and try water sports like kayaking, canoeing and paddle boarding. It will take around 2-3 hours to enjoy these activities.
You can also visit the National White Water Centre and enjoy rafting, canyoning and other outdoor activities. Spending a few hours in the center will be worth it.
If you're interested in history, visit the Bala Lake Railway which will take you on a scenic tour of the area, including the ruins of Castell Carndochan. This will take around 2 hours.
For a relaxing day out, head to the Plas yn Dre town house and gardens, which will give you a peek into the history of Bala. You can spend around 1-2 hours exploring the gardens and the house.
As for places to stay, you can consider staying at the Pale Hall Hotel or the Lake Vyrnwy Hotel and Spa. The Hand Hotel and the Royal Ship Hotel are more affordable options.