New with a few questions

@Needtolearn. I would start with the Helix SYN. It is middle of the road, it also has softer tabs so is more forgiving. It is generally not a good idea to sit whilst an Aneros is inserted as it adds a unpredictable pressure. They are designed to be entirely controlled by the bodies muscles. I have had sex with one inserted. Many find it heighten the pleasure. Health benefits are huge especially as males age, even if you don't super O. You may need to keep an open mind regarding publication. Many have reactions to water based lubes that rather spoil the show. ( You can't use silicone lub with the SYN). Most folk have a selection of Aneros models. So from the Helix SYN you can go bigger or smaller, ot choose a hard plastic model. Currently I am using two, one a bit larger Progsm Jnr, and one larger again Progsm Ice. The SGX is the smallest prostate massager. I used one of these for a long time. Others much wiser with also respond.

Is the Helix a good first massager to start with?YES, the Helix is an excellent model to begin with but for further information I'd recommend you read the thread The Best Aneros model is...How difficult is it to have the Helix and Peridise inserted and "lounge" around the house?There will probably be no difficulties with using the Peridise model in any position while lounging or making love. The Helix, however, presents some problems due to the handle/tail and P-tab arm. As @isvara noted, the design of the Aneros massagers relies upon their free, unencumbered movement to be most effective. Any body position which entails contact of your Aneros with some kind of restriction (i.e. a chair, a pillow even another body) will have an adverse effect on performance, perhaps even to the point of causing injury. Some of this can be mitigated by cutting the curl off the handle/tail but even then any body position/contact which applies external forces to the massager will affect the performance.
How difficult is it to keep them inserted while making love and are there certain positions that we'd not be able to use?Initially, until your muscles are toned up, it is possible your massager may be ejected during orgasmic contractions but you will soon be able to get that under control. As I noted above the same restrictions of body positions which apply to solo play would apply to partner play as well.
Good Vibes to You !

isvara and rumen, thank you, that's the type information I was looking for.

NTL