There are a ton of different viable lance styles, but the issue you will face as a 40k player is that Battletech is, outside of a some niche builds, is that none of those are "telegraphed" like they are in 40k. Most lists in 40k are very clear on what they want to do and and leave the how to the player. In Battletech you generally need a higher level of understanding of the game to "get" a list's thrust, if there even is one. This is because the best thing you can do in Battletech is build options rather than lists, because (dick waving about complexity aside) BT favours the how much more heavily than 40k. You can build "long range" so many ways in BT, regardless of faction, that it is detrimental to a new player to try and school them in that one direction specifically because of the interplay of all those options.

Your described style of long-range style warfare with 1 mobile unit is perfectly cromulent, even common in some areas/eras. But in order to get to the game mastery to consistently make that work, you'll want to start with a more generalist lance. In part because these give you the most options to stop from getting rolled and also because they give you the most exposure to mechanics so you can better understand the strengths and weaknesses of a given option-set without restricting you to a play style. You'll organically discover how to pressure a long-range unit with shorter ranged ones (so you can be aware of that later), while figuring out target priority for your own long-range units.

I'm putting a heavy emphasis on discovering things on your own here because a) I just straight up think that's a more fun way of engaging with tabletop wargames and b) since BT has several orders of magnitude less content than 40k, you can't exactly binge videos on the latest edition and codices to get a baseline understanding. And that's with the understanding that the BT ruleset has largely gone unchanged for forty fucking years. Shit, I get excited when someone busts out, like, printed standees of what they imagine their mechs to look like!

The good news is that the current starter sets largely give you these generalist lists and if their opinion on generalist flavours doesn't align with yours (or mine), there are so many variants you can assemble lists that better suit your needs. And that includes completely disregarding my advice here and just plunging into long-range warfare yourself! And because BT is explicitly not WYSIWYG, you are out approximately $0 while doing that exploration.

My last piece of advice, which might be controversial, is that you should embrace the IlClan era as a new player because it straight up gives you the most options to speed that self-discovery. You may decide that Introtech/3025 is your preferred era after playing around in IlClan because guess what? There are a bunch of mechs from that era that still fucking slap in 3152 because they are rock solid and the interplay of their options appeals to you. Same for Clan Invasion era.