There are all kinds of gadgets out there for training, and if properly used, I’m sure they work.
I have a tendency to keep thing s simple here: Several crates for car and house, leads, training collar, retrieving bumpers, at least two place boards and a whistle.
I use a British style Slip Lead. I also like a pinch collar attached to a 6’ lead, especially for large, powerful dogs. I use a whistle to deliver commands when I am working dogs in the field.
The whistle I like is an Acme British style 211 ½ Spaniel whistle. This delivers a variety of tones easily, and is not obnoxiously loud. For retriever training I like an Acme Thunderer.