No need to use Bigpay lah, use HLB Wise.

Assume RM1000 to TNB , use PB VS to top up BP/Boost - RM1000.
Cost to cashout RM1000 from BP/Boost - RM2 or 0.2%

Use PB VS to top up Bigpay and then pay MyTNB - RM1000,
You will gain RM60 (from PB) + RM0.70 (from Bigpay) = RM 60.70

Use PB VS to top up Bigpay and then cash-out, use HLB Wise to pay MyTNB,
You will gain RM60 (from PB) - RM2 (average, charged by BP) + RM2.50 (from HLB) + RM0.20 (from BP) = RM60.70 (or more if you can withdraw >RM3000 from ATM)

IMO, OCBC Titanium (1% unlimited), HLB Essential (0.4%/1%) are better choice till TNB bills can be paid via Boost.

Can I balance transfer HLB BT account to another bank cc?

Now reduced to RM98.
Not waivable.

Those OG will know. Back in the days you need a minimum spend of RM 2k/month to get cashback and also unwaivable AF of RM 160.