Hello! I know in our part of the world this type of backpack is the most common for birds (Americans have access to fancy Pak-o-Birds, which are unbelievably hard to find over here - I had to get my backpack sent overseas by my parents and it cost quite a bit).
I think the backpack you found is ok, if you made some changes to it after buying it. I'd replace the metal perch inside with a wood perch - that way your cockatiel can grip easier when being bounced around in the backpack. I would also mostly use it when the weather is somewhat cooler (I see you're in Maldives, which is hot and humid all year round like my current country) because the plastic will likely heat up the inside of the backpack. If you use it during normal hot weather, just be sure to keep an eye on your little one in case he starts to overheat.
I like that you're going for a carrier - sometimes just a leash is a bit scary for some birds. Inside a carrier, they can feel a bit safer from strangers and less likely to spook off. If you're using the type of leash I think you might be using, some birds will actually remove it themselves and fly away. So a carrier is definitely a safer option
