What tools are best for checkout A/B testing?

As a Shopify store owner, I've been obsessed with understanding why customers abandon their carts. My conversion rate has been hovering around 2-3%, which feels painfully low considering the money I'm spending on ads. Every abandoned cart is literally money walking away. I've tried generic optimization tactics, but nothing seems to move the needle consistently. My checkout process looks clean, but something's clearly not clicking with customers. Are they getting cold feet? Is the form too complicated? Are there hidden friction points I'm not seeing? I need a systematic way to test different checkout layouts, form designs, and psychological triggers that might convince more visitors to complete their purchase. Just a 1-2% improvement could dramatically change my store's profitability. I'm looking for robust A/B testing tools that integrate seamlessly with Shopify, provide statistically significant insights, and help me understand exactly what's preventing customers from converting.