Attribution Model - GA4 and Klaviyo

I have a couple of questions around attribution …

Firstly, what attribution model does Klaviyo use?

Secondly, what attribution model is recommended for GA4? 

(I am using Data Driven for reporting attribution model, Paid and organic channels for channels that can receive credit, 30 day window for click through conversions, 90 days for all other conversion events and 3 days for engaged view conversions)

I understand Klaviyo and GA4 will never exactly match, but I am experiencing a circa 150% discrepancy. 

When I compare GA4 to Google Ads I am getting a circa 5% discrepancy. 

Thanks