You can check this online or via app.

Unless you have USD preloaded into your Wise card, both cards apply the Visa exchange rate when you swipe overseas as it works as a Visa debit card. Both cards will also charge additional fees. Check their site for details.

Bigpay states they charge a 1% fee, so you can calculate yourself from that..

I just realised in BigPay > International transfer > it doesn't support a lot of currencies... Including USD, JPY. So I can't check their rate. But before the pandemic in 2020, I was able to use it in Japan and got spot rate conversions every transaction I made. I don't remember if, at that time, JPY was in the list of international transfers...

I can tell you at that time way back then for JPY, the rate was pretty good la. But please don't take my word for your case as it's been years + different currency... Even for SGD, I find BigPay to be sorely behind other fintech rates since 2022, even though it used to be my main method in 2020-early 2021 ish? It was better than TransferWise, old name at that time lol.

Anyway, all that aside... refer to this page: https://wise.com/my/blog/bigpay-card-malays...pay-card-limits
BigPay spot rate conversion is calculated based on the payment network processor rates, and some additional network charges which has no transparency to us:
https://www.visa.com.au/support/consumer/tr...calculator.html
https://www.mastercard.com/global/en/person...t-currency.html
I tried for both 100 USD, 1% bank rate yesterday, I saw
Visa RM 466.21
MasterCard RM 466.18 (slightly better, also as advised by my colleagues that MasterCard has better rates for more currencies).
BigPay uses MasterCard while Wise uses Visa.

Lastly, if you're good at reading market trend then
If USD is strengthening / MYR weakening: exchange asap lump sum so you lock in the rates.
Otherwise, spot rate better.