You can use jalapeños if you wish or another kind of pepper if you prefer. Because everyone's palates are different, what one person finds unbearably spicy another might consider medium-spicy. I wouldn't go the whole hog with Scotch bonnet peppers but there are plenty of different mild to moderately spicy chillies to choose from. Jalapeños are nice because they're usually pretty mild and won't overpower the more delicate fruity flavours in the jam. You can always make two separate batches - one mild version and one hotter one. If you've accidentally made it too spicy, add more sugar. This is a clever way of counterbalancing the heat. Then if you are making a cheese or charcuterie board you can offer both kinds (clearly labelled!) and people will choose which they think they'll like most.